docs: record dated dividend cash-flow ledger session (2026-08-27)

docs/engineering-log.md

@@ -99,3 +99,4 @@
 - Follow-up (A+B): theme surprises now weight-normalized by total |weight| so cross-theme magnitudes are comparable (retail 0.189->0.145). Added append-only `FactorHistory` store (`data/factor_history/<key>.jsonl`) that records every FACTORS value each scheduler run, wired into `refresh_all` (non-fatal), plus `/api/v1/learning/factors` readiness endpoint. Macro/demographic factors start at n=1 and become learnable (P4) as history accumulates. 233 tests pass.
 - Backtest accounting remediation (2026-08-27): deterministic flat-price tests exposed that ending holdings value was reported as `price_pnl` and the dividend proxy was excluded from final value/net return. The corrected identity is `final_value = capital + price_pnl + dividend_income`; API now emits `dividend_method=final_holdings_yield_proxy`, and both result/history UI paths label the proxy and warn when `leakage_guard=false`. RED failures reproduced `price_pnl=20,000/49,000`; GREEN verification: 239 backend tests, compileall, Vite build, npm audit 0 high-severity vulnerabilities, served-bundle disclosure check, static scan and diff check passed. Fresh final independent review `deleg_10918fed` passed with empty blocker arrays. Evidence: `docs/engineering-log/2026-08-27-backtest-accounting-remediation.md` and `docs/test-evidence/2026-08-27-backtest-accounting-remediation.md`. The dividend model remains a proxy and the default public backtest remains descriptive non-PIT.
 - PIT factor store + partial score provider (2026-08-27, commit `1f630be`): added `factor_vintages.py` (append-only PIT factor store: observed/released/retrieved_at + SHA-256 hash chain; `value_at(as_of)` anti-look-ahead, fail-closed when nothing released by as_of) and `pit_scorer.py` (`PitScoreProvider.score_board(as_of)` + `make_pit_score_fn`). `backtest._resolve_scores` now sets `leakage_guard=True` only when the supplied score_fn asserts `pit_meta.pit=True` (closes "any callable ⇒ PIT"); `/api/v1/backtest` accepts `use_pit`. Empty factor store fail-closes (live probe `leakage_guard=false`). Full backend **255 passed** (was 239). Honest scope: theme dimension PIT from this store forward; no factor history before 2026-08-27 so pre-today backtests stay non-PIT; siamchart fundamental partial (EPS 5-yr series PIT-grade, ratios current → `partial_pit`). Next: dated dividend cash-flow ledger.
+- Dated dividend cash-flow ledger (2026-08-27, commits `068dff2` + `5b8b6d1`): added `dividend_ledger.py` (per-symbol dated store: ex_date/record_date/pay_date/per_share/source/estimate flag; `credit_dividends` credits per_share×qty when payment due, fail-closed with no entry; `build_dps_ledger` builds per-share estimate rows from siamchart ratios.DPS). `run_backtest` accepts `dividend_ledger` and reports `dividend_method` = `dated_ledger` (real rows) | `dps_annual_proxy` (estimate) | `final_holdings_yield_proxy` (legacy). `/api/v1/backtest` accepts `use_ledger`. Frontend maps method to an honest Thai label + Proxy badge on result card and history rows. Full backend **266 passed** (was 255). Honest scope: DPS rows are estimates (no ex-date history in snapshot yet); real dated cash flows require collecting per-stock dividend history, which upgrades a symbol to `dated_ledger`.