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+# Phase W4 — Insights sub-pages restructure + Sleep + batch-delete (v1.4.25)
+
+Scope: W4a (routed sub-pages) + W4b (DELETE endpoint) + W4c (Sleep
+sub-page) + W4d (mother-page restructure) + W4e (i18n strings).
+Branch: `develop`. No push, no tag, atomic commits.
+
+## Commits
+
+1. `38bbba1` — `feat(insights): scaffold 6 metric sub-pages with shared layout shell`
+2. `959adec` — `feat(api): DELETE /api/measurements/by-external-ids for iOS deletion-sync`
+3. `cb825ec` — `feat(insights): new /insights/schlaf sub-page with sleep-stage chart`
+4. `7644bd0` — `refactor(insights): mother page hosts overview only; metric depth moves to sub-pages`
+5. `d63fa27` — `i18n(insights): EN + DE strings for the 7 insights sub-pages`
+6. `85e93dc` — `chore(openapi): regenerate docs/api/openapi.yaml` (reconciles a W7 agent's drift)
+
+## Files added
+
+- `src/app/insights/layout.tsx` — shared layout (server component shim).
+- `src/app/insights/blutdruck/page.tsx`
+- `src/app/insights/gewicht/page.tsx`
+- `src/app/insights/puls/page.tsx`
+- `src/app/insights/stimmung/page.tsx`
+- `src/app/insights/medikamente/page.tsx`
+- `src/app/insights/bmi/page.tsx`
+- `src/app/insights/schlaf/page.tsx`
+- `src/app/api/measurements/by-external-ids/route.ts` — DELETE handler.
+- `src/components/insights/insights-layout-shell.tsx` — owns the
+  advisor query at the layout level so the regenerate button works
+  on every sub-page.
+- `src/components/insights/sub-page-shell.tsx` — title + badge +
+  focusable h1 (a11y focus restoration on tab navigation).
+- `src/components/insights/sleep-duration-chart.tsx` — wrapper around
+  `<HealthChart chartKey="sleep" />`.
+- `src/components/insights/sleep-stage-stacked-bar.tsx` — Recharts
+  horizontal stacked bar of stage composition.
+- `src/components/insights/sleep-overview.tsx` — sleep page composition.
+- `src/hooks/use-insights-layout-prefs.ts` — `comparisonBaseline`
+  reader (single source for every Insights surface).
+- `src/lib/insights/sub-page-metric.ts` — slug → MeasurementType[] map.
+- `tests/integration/measurements-batch-delete.test.ts` — 4 cases.
+- `src/components/insights/__tests__/sleep-stage-stacked-bar.test.tsx` — 4 cases.
+- `src/components/insights/__tests__/sub-page-shell.test.tsx` — 3 cases.
+
+## Files modified
+
+- `src/app/insights/page.tsx` — slim mother page (1498 lines removed).
+- `src/components/insights/insights-tab-strip.tsx` — route-aware
+  (`<Link>` + `usePathname()` replacing scroll-into-view).
+- `src/lib/openapi/routes.ts` — DELETE endpoint registered.
+- `docs/api/openapi.yaml` — regenerated.
+- `messages/en.json`, `messages/de.json` — sub-page descriptions,
+  empty-state CTAs, sleep stage labels.
+- `src/app/__tests__/insights-polish.test.ts` — two guard tests
+  re-pointed at the new homes of their assertions (layout shell +
+  shared layout-prefs hook).
+- `src/components/insights/__tests__/trends-row.test.tsx` — every
+  render now wraps in a TanStack-Query provider because the W7
+  timezone agent added a `useAuth()` call inside `<TrendsRow>`.
+
+## Architectural notes
+
+- **CoachDrawer placement** stays on the mother page body only.
+  Navigating to a sub-page unmounts the drawer (Marc's directive). The
+  layout shell deliberately does NOT mount the drawer.
+- **Per-card chart cog**: every sub-page passes a `chartKey` from
+  `CHART_OVERLAY_KEYS` so the existing dashboard chart-cog surface
+  applies on Insights without a single backend change.
+- **`comparisonBaseline` plumbing**: `useInsightsLayoutPrefs()` is now
+  the single shared reader; the mother page no longer touches it
+  because its charts moved out.
+- **OpenAPI**: the new `MeasurementsDeleteByExternalIdsRequest` /
+  `MeasurementsDeleteByExternalIdsResult` schemas live alongside the
+  ingest pair; the path entry sits under the Measurements tag.
+
+## Test delta
+
+- Unit + integration tests outside `tests/integration/` go from 2365
+  → 2375 (+10), all passing.
+- New integration suite `measurements-batch-delete.test.ts` adds 4
+  cases (requires Postgres; not run locally per project convention).
+
+## Verification
+
+```
+$ pnpm typecheck    # exit 0
+$ pnpm lint         # clean (no warnings on my files)
+$ pnpm openapi:check  # spec in sync
+$ pnpm vitest run --exclude='tests/integration/**'
+  Test Files  277 passed (277)
+  Tests       2375 passed | 1 skipped (2376)
+```
+
+`pnpm format:check` still surfaces 21 pre-existing warnings in
+parallel-agent files (planning markdown, mood-related modules,
+admin login-overview tests). My files all pass; the unrelated drift
+is out of W4 scope.
+
+## Manual verification (not run locally)
+
+Manual smoke notes to verify after deploy:
+- `/insights` mother page renders (Hero + Briefing + Trends + Advisor +
+  Coach drawer).
+- Each of `/insights/{blutdruck,gewicht,puls,stimmung,medikamente,bmi,schlaf}`
+  renders without crashes and the tab strip's active pill matches.
+- Chart-cog on a sub-page chart persists overlay prefs across
+  refreshes (`PUT /api/dashboard/chart-overlay-prefs` round-trip).
+- AI-disabled user (demo) doesn't see broken Coach buttons — the
+  layout shell forwards `regenerate` only when authenticated, and the
+  per-section status cards already gate on `hasProvider`.
+- Sleep sub-page empty-state (no SLEEP_DURATION rows) renders the
+  "Apple Health sync in v1.5" CTA.
+
+## Deferred / not in scope
+
+- Per-night stacked column chart (true time-series view of stages).
+  The W4c chart shows the 30-day composition aggregate the existing
+  `/api/analytics` endpoint already exposes; a per-night view would
+  need a new server endpoint with per-day×stage data. Park for v1.4.26
+  in `.planning/v1425-backlog.md` if Marc wants it.
+- `/api/insights/general-status` endpoint is now orphaned (no
+  consumer survives the mother-page slim-down). Server route +
+  associated translations weren't removed in this phase to keep the
+  surface area tight; W4 ships orchestration only.
+- The `insights.navGeneral` translation key is still referenced from
+  the legacy `SECTION_LABEL_KEYS` map but the new route-aware strip
+  doesn't read it. Safe to delete in a follow-up cleanup.
+- Greying out the comparison overlay picker when prior-period data is
+  unavailable (research §4 polish; not required to ship).
+
+## Constraints honoured
+
+- No version bump or CHANGELOG entry (W11 owns release notes).
+- No edits to `src/lib/ai/coach/snapshot.ts` (W7b in flight).
+- No edits to `src/components/insights/coach-panel/coach-drawer.tsx`
+  internals.
+- No edits to chart-tokens / recommendation-card / insight-advisor
+  internals (W5b in flight).
+- No edits to admin login overview (W8b in flight).
+
+## Risk notes for reviewer
+
+- The layout shell mounts `useInsightsAdvisorQuery(isAuthenticated)`
+  on every Insights surface. The query's `staleTime: 60 * 60 * 1000`
+  (60 min) prevents network thrash; re-mounting on tab navigation is
+  a cache read.
+- The mother page's `<HeroStrip onRegenerate>` wiring is GONE — the
+  hero band's regenerate button no longer paints. The strip-mounted
+  regenerate icon is the sole page-level affordance.
+- `DELETE /api/measurements/by-external-ids` bypasses the
+  `Idempotency-Key` cache. A retried DELETE returns the same
+  `deletedCount: 0` because the rows are already gone — that's the
+  correct contract; the client should treat both calls as success.