docs: capture H-series learnings in project memory

Recurring Issues & Patterns: EF migration generation via dotnet ef + the
migrations-remove snapshot hazard, Sports.Code ValueGeneratedNever, validated
get-only record props blocking `with` (CS0200), and the JsonSettingsWriter
section-replace secret-clobbering gotcha + UI-mirror-options pattern.

New "Analysis Hardening (H-series)" learnings: the 4-detector fan-out +
IsDirectional() gate, SavedStrategy NOCASE name collation, and the config-gated
paper-trading worker.

CLAUDE.md

@@ -121,6 +121,26 @@ Marathon_<YYYY-MM-DD>_to_<YYYY-MM-DD>.xlsx
 - **`Event.ScheduledAt` requires offset `+03:00`.** Test fixtures and any code
   that constructs Moscow datetimes must use `new DateTimeOffset(date, TimeSpan.FromHours(3))`,
   never pass a `DateTime.UtcNow` value to that constructor.
+- **EF migrations — generate with `dotnet ef`, do NOT `migrations remove`.**
+  `MarathonDbContextFactory` is a self-contained design-time factory, so
+  `dotnet ef migrations add X --project src/Marathon.Infrastructure --startup-project src/Marathon.Infrastructure`
+  works. AVOID `dotnet ef migrations remove`: older migrations were hand-written without a
+  Designer snapshot, so remove blanks `MarathonDbContextModelSnapshot.cs` and the next `add`
+  regenerates the WHOLE schema. Validate a migration on a throwaway DB with
+  `dotnet ef database update --connection "Data Source=<ABSOLUTE>/data/_migtest.db"` (absolute
+  path — EF resolves relatives from the build-output dir, not the shell cwd; create `./data/` first).
+- **`Sports.Code` is `.ValueGeneratedNever()`** — it's the bookmaker's natural sport id
+  (6/11/22723…), not an autoincrement surrogate. Without it EF's int-PK convention emits a
+  spurious AUTOINCREMENT `AlterColumn` on every migration.
+- **Validated get-only record properties block `with`** (CS0200): `BacktestStrategy.MinScore`,
+  `PaperBet.Rate`/`Stake` are re-declared with validation, so build a new instance instead of
+  `with { ThatProp = … }` (you can still `with` the un-redeclared props, e.g. `SavedStrategy with { Strategy = … }`).
+- **`JsonSettingsWriter.SaveSectionAsync` replaces the whole section** (`root[section]=json`),
+  so a Settings-UI save drops any key not on the form. Never surface a secret-bearing section
+  (e.g. `Notifications` → Telegram token) in the UI — it would wipe the secret from
+  `appsettings.Local.json`. To surface a non-secret section, add a mutable mirror options class
+  in `Marathon.UI.Services` bound to the same section name (UI can't reference Infrastructure's
+  options types — same pattern as the two `WorkerOptions`).
 
 ## Feature: Initial Implementation > Phase 4: Application + Workers — Learnings
 
@@ -203,3 +223,25 @@ For full detail see `spike/SCRAPE_FINDINGS.md` and `spike/SCHEMA_DRAFT.md`.)
 - **Signal-red is the load-bearing alert tone** for Phase 7. Use
   `var(--m-c-anomaly)` exclusively (never raw `#dc2626`). Pulsing animation
   (`m-pulse`) MUST respect `prefers-reduced-motion`.
+
+## Feature: Analysis Hardening (H-series) — Learnings
+
+- **Anomaly detectors are a fan-out array in `DetectAnomaliesUseCase`** — 4 now
+  (`SuspensionFlip`, `SteamMove`, `SuspensionFreeze`, `OverroundCompression`). A new detector
+  implements `IAnomalyDetector`, reuses `MatchWinEvidence` for the canonical evidence JSON
+  (so the parser + outcome evaluator work unchanged), and is added to that array. Continuous
+  sliding-window detectors (steam, overround) emit at every `end` and skip suspension-sized
+  gaps so they never overlap the across-suspension flip/freeze detectors.
+- **`AnomalyKind.IsDirectional()` gates staking/grading** — flip + steam are directional
+  (predict a side); freeze + overround are informational and are excluded from the backtest
+  (`RunBacktestUseCase`) and the outcome evaluator so they don't skew hit-rate/score calibration.
+- **`SavedStrategy` (backtest presets) use NOCASE name collation** — the unique index AND
+  `GetByNameAsync` both fold case (column-level `UseCollation("NOCASE")`), so save-by-name
+  upserts rather than creating "Kelly"/"kelly" duplicates. Domain stores stake fractions; the
+  form/VM speak percent — convert ×100/÷100 at the UI boundary.
+- **Paper-trading (forward-test) is a config-gated worker** (`PaperTrading:Enabled`, default
+  false; tunable on the Settings page). `PaperTradingWorker` opens flat-stake `PaperBet`s on
+  new directional anomalies (unique on `AnomalyId`; baseline since-marker advances only after a
+  successful open pass; settle runs in its own catch so a settle failure can't strand the
+  marker) and settles them against results (Won iff pick == winner). `/paper-trading` shows
+  settled-only P&L. The ledger is FK-free (survives snapshot-retention pruning), like `PlacedBets`.