fix(backtest): address the second review of the breakeven and book-config work

- The breakeven study grades at the shadow book's capacity AND risk per
  trade, and labels each with where it came from. A missing setting row
  now reads "shadow_book default" instead of crediting the setting; the
  committed report said shadow_book_capacity though the snapshot has no
  such row.
- _production_book_config reads strategies through the same
  _portfolio_monitor_strategies() hook as the monitor.
- breakeven_gate_reset is rejected when there is no post-stop episode or
  cooldown for it to start, and the study skips its diagnostic arm for a
  book without one, so a production config change cannot abort the run.
- identical_to_control is renamed ties_control_on_graded_metrics and needs
  real values: be_2r ties on every graded metric but still changed 2 trades.
- _BookConfig drops an unused field and hashes by identity; the min-R:R
  sweep swaps its gate in with dataclasses.replace instead of passing it.
- New tests cover the parity guard's success path, the no-config fallback
  and the gate-reset check.

The breakeven report is regenerated: every row, diagnostic row and the
parity check are identical; only the labels, the risk fields and the
renamed flag changed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/research/residual-normalization-findings.md

@@ -55,6 +55,10 @@ long-only, gated, capital-constrained production book.
   calendar overlap, and an end-to-end screen check. Ruff passed for the runner
   and its tests. The existing Python runtime was usable outside the filesystem
   sandbox; no environment replacement was needed.
+- A 2026-10-10 code review added four tests (missing prices, file release,
+  paired-coverage guard, source ids) with the runner fixes they cover. The
+  report was regenerated with the fixed runner; its screen results are
+  byte-identical to the original run.
 
 **Interpretation and decision**