fix: period close sweeps only through the period end; partnerships close into members' capital

The close zeroed every revenue and expense account's all-time movement,
so closing a period after later entries were posted swept those too:
close January in March and February's and March's income landed in
January's closing entry. The preview had the same bug and never showed
where the net went. Now:

- close_period_to(id, to) zeroes balances as of the period end; entries
  dated later stay open for their own period. Periods must close in
  order (LedgerError::CloseOutOfOrder): a later close has already swept
  the earlier period.
- CloseTo::Members: for a partnership (multi-member LLC) the net goes to
  each member's capital account by share, to the cent, the last member
  absorbing rounding, which is what K-1 capital accounts track.
  CloseTo::RetainedEarnings (3999) stays the default; close_period is
  shorthand for it. books.close_period picks Members when
  wanderbooks.toml lists members.
- The journal records the close target; replay re-derives the closing
  entry and now compares every line with the journal, not just the id,
  so a change to closing math can never silently rewrite history.
- The tool's preview is the real close run on a clone of the ledger
  (Ledger now derives Clone), so preview and post can't disagree.
- Members' equity: closing entries into a capital account are income,
  not contributions. Balance sheet for a partnership: capital accounts
  (with allocated earnings), then only unallocated earnings —
  "Undistributed earnings, prior years" if any, and this year's unclosed
  net income (loss). periods::allocate is shared by the close and the
  statement.

Tests: January closed after February is posted sweeps exactly Dr 4000
2,500 / Cr 6100 800 / Cr 3999 1,700 (mutation-checked: the old code gives
3,500/120/800/2,580); out-of-order close refused; a partnership close
splits 666.67 into 333.34/333.33 with no 3999, and the members' equity
statement reads correctly before and after; store replay of a members
close (reopen, rebuild, verify); partnership and corporate balance sheet
layouts; stdio close preview equals the posted lines.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtYEaR6M6Ybdhm6X98BWNu

docs/requirements.md

@@ -111,8 +111,16 @@ requirement conflict, the requirement wins.
   Reports work in base currency. (Full per-account currencies and translation
   remain future.)
 - **R-? — Periods and close.** Was R-FUTURE-2.
-  `ledger-core::periods`: `create_period`, `close_period` (posts closing
-  entry to `3999` Retained Earnings), closed periods reject new entries.
+  `ledger-core::periods`: `create_period`, `close_period_to(id, to)`; closed
+  periods reject new entries. The closing entry, dated at period end,
+  zeroes each revenue and expense account's balance **as of the period
+  end** (later-dated entries belong to later periods) and puts the net in
+  `to`: `CloseTo::RetainedEarnings` (`3999`, the corporate convention;
+  `close_period` is shorthand) or `CloseTo::Members` (each member's capital
+  account by share, to the cent, the last absorbing rounding: the
+  partnership convention). Periods close in order (`CloseOutOfOrder`). The
+  journal records the target, and replay re-derives the closing entry and
+  checks every line against the journal.
 - **R-? — A/R and A/P workflows.** Was R-FUTURE-5.
   `ledger-core::arap`: customers, vendors, invoices, bills, payments,
   AR/AP aging. MCP tools for the full workflow.