docs(balance): ADR 0015 + guide + architecture + CHANGELOG for per-security detail (#218)
Final docs link of the Étape 2 stack (#210-#217).
- ADR 0015 (Accepted): holdings-per-snapshot model; aggregated-line-is-source-of-truth invariant (why non-breaking, cites ADR 0008 Modified Dietz per account); transaction-based alternative rejected (PP PR #779); latent gain vs per-security Modified Dietz (out of scope); detailed_since authoritative pivot; security-immortal-once-referenced (ON DELETE RESTRICT). Mirrors ADR 0014 structure.
- Guide: new 'Détail par titre' section in docs/guide-utilisateur.md (per-security entry, detail-account wizard, latent gain) + matching docs.balance.* i18n keys (FR + EN, in-app guide surface).
- architecture.md + CLAUDE.md: reconciled stale DB counters to real values — 20 tables / 24 indexes / 16 migrations (were 13/15/7 and 18/16/v9). Étape 2 delta: +2 tables (balance_securities, balance_snapshot_holdings) + 2 indexes + migrations v14/v15/v16. Backfilled v10-v16 in the migrations table, ADR table (0012 Rejected, +0013/0014/0015), new securities/detailed-save/latent-gain service surface.
- CHANGELOG.md + CHANGELOG.fr.md [Unreleased]: extended with #215 (wizard), #216 (drill-down + latent gain), #211 (auto-conversion note); did not duplicate #214's per-security entry. Bilingual parity.
Docs-only: no production TS/Rust logic touched. Gate green: build (tsc+vite) + 627 tests pass.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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