fix(compiler): React Compiler safety triage — 5 categories cleared

Cleared 4 rule buckets (37 violations, including 5 real bugs) and
silenced 1 informational bucket from the Next 16 / react-hooks v7
upgrade. Cleared rules promoted from `warn` back to `error` so new
regressions block CI.

Real bug fixes:
- `interest-contact-log-tab.tsx`: `useMemo` used for side effects
  (5 setState calls inside a memo body); converted to `useEffect`.
- `PieChart.tsx`: cumulative `let angle` mutation in a render-phase
  `map`; converted to `reduce` so the slice array is built without
  re-assignment.
- `documents-hub.tsx`: `useMemo(() => ({ count: 0 }))` used as a
  mutable drag counter; converted to `useRef`.
- `notes-list.tsx`: `Date.now()` read during render for note-edit
  countdown (impure) → pinned to a `now` state ticked every 30s.
- `onboarding-checklist.tsx` / `user-profile.tsx` /
  `user-settings.tsx`: `useEffect(() => void load(), [])` with the
  `load` function declared AFTER the effect — relied on hoisting,
  trips Compiler's "access before declared" rule. Declared inside
  the effect.

Pattern fixes (intentional cache-via-ref → state or layout-effect):
- 6 `ref.current = x` writes during render moved into layout
  effects (`use-realtime-invalidation`, `settings-form-card`,
  `inbox`).
- 3 `ref.current` reads during render (search totals cache,
  scanner file ref) rewritten to backed-by-state.
- `use-is-mobile.ts` rewritten on `useSyncExternalStore` to avoid
  the SSR-then-rehydrate setState dance.
- `use-notifications.ts` rewritten to write socket pushes directly
  into the React Query cache via `setQueryData`, removing a local
  state mirror.

Rule config (`eslint.config.mjs`):
- `react-hooks/purity` → error (was warn, cleared)
- `react-hooks/set-state-in-render` → error (was warn, cleared)
- `react-hooks/immutability` → error (was warn, cleared)
- `react-hooks/refs` → error (was warn, cleared)
- `react-hooks/incompatible-library` → off (informational only)
- `react-hooks/set-state-in-effect` → warn (51 remaining, all the
  useEffect→fetch→setState data-fetch pattern; migration to
  useQuery tracked in BACKLOG)

Verified: tsc clean, eslint 0 errors / 69 warnings (down from 105),
vitest 1315/1315, next build green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/pdf/brand-kit/charts/PieChart.tsx

@@ -66,16 +66,27 @@ export function PieChart({ data, width = 240, height = 200, innerRadiusRatio = 0
   const cy = height / 2;
   const ir = r * innerRadiusRatio;
 
-  let angle = -Math.PI / 2;
-  const slices = data.map((d, i) => {
+  // Cumulative angle via reduce instead of a let-mutation: the
+  // React Compiler safety rules forbid render-phase re-assignment
+  // because it'd defeat memoization once the component is compiled.
+  const slices = data.reduce<
+    Array<{
+      d: (typeof data)[number];
+      color: string;
+      startAngle: number;
+      endAngle: number;
+      slice: number;
+    }>
+  >((acc, d, i) => {
+    const startAngle =
+      acc.length === 0 ? -Math.PI / 2 : (acc[acc.length - 1]?.endAngle ?? -Math.PI / 2);
     const slice = (d.value / total) * Math.PI * 2;
-    const startAngle = angle;
-    const endAngle = angle + slice;
-    angle = endAngle;
+    const endAngle = startAngle + slice;
     const color =
       d.color ?? DEFAULT_PALETTE[i % DEFAULT_PALETTE.length] ?? PDF_TOKENS.colors.accentBlue;
-    return { d, color, startAngle, endAngle, slice };
-  });
+    acc.push({ d, color, startAngle, endAngle, slice });
+    return acc;
+  }, []);
 
   const legendX = cx + r + 24;
   const legendStartY = cy - (data.length * 12) / 2;