Parties, attachment links, statements, reconciliations (store), TIN vault crate

Parties: one directory for vendors, contractors, customers, employees,
members, platforms, agencies, banks, landlords (ledger-core parties.rs).
W-9/W-4 facts without the number (last four only; any nine-digit run in a
party field is refused, Treas. Reg. 301.6109-4). Vendor and customer
records link to parties on replay; core tags every bill, invoice, payment,
and reversal with its counterparty. Journal events party.*,
entry.party_set; payroll lines name the employee party.

MCP: books.add_party, update_party, set_party_roles, set_w9, set_w4,
parties, party, set_entry_party; draft_entry party; run_payroll employee;
show party. Viewer: Parties directory and party pages, search, journal
text, W-9 attention, demo data.

One definition of a party's money (ledger_core::parties::activity) for
MCP and viewer. 1099 amounts count payments from cash and financing
accounts (a member paying for the company counts; a card doesn't; a
prepayment counts when made): vendor_1099_report_with, B-19.

Store: attachment links to any subject, statements, reconciliations
(schema v11), with replay and projection. ledger-vault: encrypted TIN and
W-9 records (ChaCha20-Poly1305, key file outside the books).

Spec-blind tests for parties (core, store, MCP, viewer) and attachments.

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

crates/ledger-store/src/error.rs

@@ -5,6 +5,31 @@ use thiserror::Error;
 /// Every way a store operation can fail.
 #[derive(Debug, Error)]
 pub enum StoreError {
+    /// An attachment link names a subject that doesn't exist.
+    #[error("no {0} to link to")]
+    UnknownSubject(String),
+    /// The attachment is already linked to that subject.
+    #[error("attachment {0} is already linked to {1}")]
+    AlreadyLinked(u64, String),
+    /// The attachment isn't linked to that subject.
+    #[error("attachment {0} isn't linked to {1}")]
+    NotLinkedTo(u64, String),
+    /// A statement record that doesn't fit its account or itself.
+    #[error("bad statement: {0}")]
+    InvalidStatement(String),
+    /// The books don't agree with the statement yet.
+    #[error(
+        "not reconciled: the cleared balance differs from the statement by {difference}; \
+         clear the lines the statement shows (or find what's missing) first"
+    )]
+    NotReconciled {
+        /// Cleared balance less the statement balance.
+        difference: rust_decimal::Decimal,
+    },
+    /// A reconciliation command that breaks the sequence.
+    #[error("{0}")]
+    ReconciliationRefused(String),
+
     /// An asset can't be corrected once depreciation for it is posted: the
     /// posted entries would disagree with the corrected schedule.
     #[error("asset {0} already has depreciation posted; correct it with entries instead")]