Fixed assets carry federal tax basis beside book value; tests sweep stale temp dirs

- core: TaxBasisRule (cost IRC 1012, carryover IRC 723, personal-use conversion Treas. Reg. 1.168(i)-4(b)), TaxBasis with the contributor's adjusted basis, Asset::tax_basis and ::built_in_gain (IRC 704(c)); the register gains tax rule, contributor basis, tax basis, built-in gain, total tax basis, missing count (rules.md B-25; sources vendored in docs/spec/sources/irs-partnership-basis.md)
- store: asset.tax_basis_set journaled, replayed, projected (schema v10)
- mcp: books.set_asset_tax_basis; register_asset takes tax_basis_rule and contributor_basis, checked before anything registers (found by the spec-blind suite); list_assets and the register export (json, csv) carry tax basis; instructions say to record it for every asset
- import: the register's XLSX and PDF gain the federal tax basis table with citations
- viewer: tax basis on the Assets page, the asset page (a Tax basis card), the report, the journal, and Needs attention for assets without one
- just: check and the mutation recipes sweep this user's test book dirs older than an hour (killed runs had left 23 GB in RAM-backed /tmp)
- docs: the parties, attachments, TIN vault, completeness engine, and updates designs (docs/parties-and-attachments.md)
- tests: spec-blind tax basis suites in core, store, MCP; register PDF/XLSX and viewer tests

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

docs/spec/README.md

@@ -13,7 +13,7 @@ layers differ in what they cover and in whether we may copy them:
 | Layer | What it governs | Copyright | Here |
 |---|---|---|---|
 | **Pacioli (1494), Geijsbeek translation (1914)** | The mechanics of double entry: debits equal credits, the trial balance, one money, writing only forward, correcting by opposite entry, closing into capital. No modern standard restates these; they predate every regulator. | Public domain | Vendored verbatim: `sources/pacioli-1494.md` |
-| **IRS: Internal Revenue Code, Treasury Regulations, publications, form instructions** | Records and supporting documents, retention, accounting periods and methods, information returns (1099), capitalization (de minimis, 12-month rule), partners' capital, payroll taxes, rounding on returns, return line items for tax categories (`sources/irs-tax-lines.md`) | Public domain (17 U.S.C. §105; IRS.gov's content policy) | Vendored verbatim: `sources/irs-*.md`, `sources/us-public-domain-status.md` |
+| **IRS: Internal Revenue Code, Treasury Regulations, publications, form instructions** | Records and supporting documents, retention, accounting periods and methods, information returns (1099), capitalization (de minimis, 12-month rule), partners' capital, tax basis of purchased and contributed property (`sources/irs-partnership-basis.md`), payroll taxes, rounding on returns, return line items for tax categories (`sources/irs-tax-lines.md`) | Public domain (17 U.S.C. §105; IRS.gov's content policy) | Vendored verbatim: `sources/irs-*.md`, `sources/us-public-domain-status.md` |
 | **File formats: Intuit (QuickBooks Online bank CSV, QuickBooks Desktop IIF), ECMA-376 Office Open XML, Microsoft Excel limits, Avery label sheets** | What `ledger-import` reads and writes: bank/card CSV layouts and signs, IIF journal entries, how XLSX stores numbers and Excel's 15-digit precision, asset-label sheet geometry (Avery 5160) | © Intuit Inc.; © Ecma International; © Microsoft; © Avery Products Corporation | Cited with short quotes, URLs, and hashes: `sources/intuit-bank-csv.md`, `sources/intuit-iif.md`, `sources/xlsx-numbers.md`, `sources/avery-5160.md` |
 | **FASB Accounting Standards Codification (ASC)** | Authoritative US GAAP: cash flows (ASC 230), revenue and principal vs agent (ASC 606), foreign currency (ASC 830), credit losses and aging (ASC 326), property and depreciation (ASC 360) | © Financial Accounting Foundation | Cited by paragraph with short quotes only (in `rules.md`) |
 | **FASB Concepts Statement No. 8, Chapter 4 (2021)** | Definitions of the five elements (it replaced Concepts Statement 6) | © Financial Accounting Foundation; non-authoritative | Cited with short quotes only |

docs/spec/rules.md

@@ -464,3 +464,33 @@ accounts.
 `assets::check_asset_tag`, `assets::check_serial`. **Checked:**
 `ledger-core` `tests/spec_asset_tags.rs`; `ledger-store`
 `tests/asset_tags.rs`; `ledger-mcp` `tests/spec_assets.rs`.
+
+## B-25 Tax basis beside book value
+
+**Status:** AUTHORITY (`sources/irs-partnership-basis.md`); DECISION
+(Stephen, 2026-10-15: the register carries tax basis)
+
+Book value and tax basis are different numbers for the same asset. The
+book value of a member's contribution is its fair market value (Treas.
+Reg. §1.704-1(b)(2)(iv)(d)(1), cited). Its federal tax basis follows the
+rule that applies: property the company buys has a cost basis ("The basis
+of property shall be the cost of such property", IRC §1012(a)); property a
+member contributes keeps "the adjusted basis of such property to the
+contributing partner at the time of the contribution" (IRC §723,
+carryover); property a member converts from personal use depreciates from
+"the lesser of its fair market value or its adjusted depreciable basis"
+(Treas. Reg. §1.168(i)-4(b)(1)). The difference between fair market value
+and the contributor's adjusted basis is the built-in gain (positive) or
+loss (negative) that IRC §704(c) makes the partnership account for; a
+built-in loss counts only for the contributing member (§704(c)(1)(C)).
+wanderbooks records the rule, the contributor's adjusted basis, the
+resulting tax basis, and the built-in gain or loss; tax depreciation
+(MACRS, conventions, elections) stays with the CPA (`sources/irs-depreciation.md`).
+
+**Enforced:** `Ledger::set_asset_tax_basis` / `check_asset_tax_basis`
+(cost takes no contributor basis, a contribution requires one,
+non-negative, in cents), `Asset::tax_basis`, `Asset::built_in_gain`,
+`reports::fixed_asset_register` (per-row tax fields, `total_tax_basis`,
+`missing_tax_basis`). **Checked:** `ledger-core` `tests/spec_tax_basis.rs`;
+`ledger-store` `tests/asset_tags.rs` (`asset.tax_basis_set` journaling,
+replay, v9 migration, corrupt payloads); `ledger-mcp` `tests/spec_assets.rs`.

docs/spec/sources/irs-partnership-basis.md

@@ -0,0 +1,40 @@
+# Tax basis of fixed assets: cost, contributed property, and personal-use conversion
+Governs the tax basis the fixed asset register carries beside book value (rules.md B-25). Property the partnership buys has a cost basis (IRC §1012); property a member contributes keeps the member's adjusted basis (IRC §723), and the difference from its fair market value is the built-in gain or loss that §704(c) makes the partnership account for; property a member converts from personal use has a depreciable basis of the lesser of fair market value and adjusted basis (Treas. Reg. §1.168(i)-4(b)(1)). wanderbooks records the basis; tax depreciation (MACRS, conventions, elections) stays with the CPA.
+
+## 26 U.S.C. §1012(a): basis is cost
+Source: <https://www.law.cornell.edu/uscode/text/26/1012>  
+Retrieved: 2026-10-15  
+SHA-256 of the retrieved file (`usc1012.html`): `831c9a6a91fceb2f78968520b6f7811b0975bdc170538fa333baa072b799990b`
+
+> The basis of property shall be the cost of such property, except as otherwise provided in this subchapter and subchapters C (relating to corporate distributions and adjustments), K (relating to partners and partnerships), and P (relating to capital gains and losses).
+
+## 26 U.S.C. §723: basis of property contributed to a partnership
+Source: <https://www.law.cornell.edu/uscode/text/26/723>  
+Retrieved: 2026-10-15  
+SHA-256 of the retrieved file (`usc723.html`): `bfc8c78b5ef5e230f8df1c76d8ab3020ea4a515d987576bba37e740bb5c8c4c7`
+
+> The basis of property contributed to a partnership by a partner shall be the adjusted basis of such property to the contributing partner at the time of the contribution increased by the amount (if any) of gain recognized under section 721(b) to the contributing partner at such time.
+
+## 26 U.S.C. §704(c)(1): built-in gain and loss on contributed property
+Source: <https://www.law.cornell.edu/uscode/text/26/704>  
+Retrieved: 2026-10-15  
+SHA-256 of the retrieved file (`usc704.html`): `03a2c2fd087cc5e849f3755417e34bf8d869afc67e4650f5473a4e73b7cec099`
+
+**§704(c)(1)(A): the variation between basis and fair market value**
+
+> income, gain, loss, and deduction with respect to property contributed to the partnership by a partner shall be shared among the partners so as to take account of the variation between the basis of the property to the partnership and its fair market value at the time of contribution,
+
+**§704(c)(1)(C)**
+
+> if any property so contributed has a built-in loss — (i) such built-in loss shall be taken into account only in determining the amount of items allocated to the contributing partner, and (ii) except as provided in regulations, in determining the amount of items allocated to other partners, the basis of the contributed property in the hands of the partnership shall be treated as being equal to its fair market value at the time of contribution.
+
+**Built-in loss, defined**
+
+> For purposes of subparagraph (C), the term “built-in loss” means the excess of the adjusted basis of the property (determined without regard to subparagraph (C)(ii)) over its fair market value at the time of contribution.
+
+## Treas. Reg. §1.168(i)-4(b)(1): conversion from personal to business use
+Source: <https://www.ecfr.gov/api/renderer/v1/content/enhanced/current/title-26?part=1&section=1.168(i)-4>  
+Retrieved: 2026-10-15  
+SHA-256 of the retrieved file (`ecfr168i4.html`): `284efb83eeb11442ab86e050f6d630bd468fd75463e27e3ec81dbc8de455e9be`
+
+> Depreciation deduction allowable. This paragraph (b) applies to property that is converted from personal use to use in a taxpayer's trade or business, or for the production of income, during a taxable year. This conversion includes property that was previously used by the taxpayer for personal purposes, including real property (other than land) that is acquired before 1987 and converted from personal use to business or income-producing use after 1986, and depreciable property that was previously used by a tax-exempt entity before the entity changed to a taxable entity. Except as otherwise provided by the Internal Revenue Code or regulations under the Internal Revenue Code, upon a conversion to business or income-producing use, the depreciation allowance for the year of change and any subsequent taxable year is determined as though the property is placed in service by the taxpayer on the date on which the conversion occurs. Thus, except as otherwise provided by the Internal Revenue Code or regulations under the Internal Revenue Code, the taxpayer must use any applicable depreciation method, recovery period, and convention prescribed under section 168 for the property in the year of change, consistent with any election made under section 168 by the taxpayer for that year (see, for example, section 168(b)(5)). See §§ 1.168(k)-1(f)(6)(iii) or 1.168(k)-2(g)(6)(iii), as applicable, and 1.1400L(b)-1(f)(6) for the additional first year depreciation deduction rules applicable to a conversion to business or income-producing use. The depreciable basis of the property for the year of change is the lesser of its fair market value or its adjusted depreciable basis (as defined in § 1.168(b)-1T(a)(4)), as applicable, at the time of the conversion to business or income-producing use.