feat(insights): mood calendar and chart arrive together; add via the header plus

On /insights/mood the line chart used to paint first and the calendar,
whose aggregate is the slower read, pushed it down when it landed
(CLS 0.16 at 390 px on a cold load). The page now holds both on
final-height skeletons until the chart's read has settled and the
calendar's has landed, then shows them in the same frame. The calendar's
height is written in container-query units, so its box is the right size
from the first paint, in the skeleton and the painted grid alike. A
server wrapper prefetches both reads in parallel (time-boxed, skipped
under a record switch, off when SSR prefetch is off), so on a warm cache
they are in the first HTML. The route and the prefetch share
`moodInsightsWire`, so the seeded cell is the route's shape.

The "Log a mood entry" and "Take a mental-wellbeing check-in" text links
under the heading are gone. Logging is the header plus, which opens the
mood form in place; the check-in keeps its own place in the navigation.
The plus is one shared component, `SubPageAddButton`, now also behind
the measurement pages' capture link and the workouts page, which drew
its own. An audit of every Insights page found no other text add-button
of this kind; the remaining buttons are empty-state calls to action.
A sweep keeps it that way.

`e2e/v142-qol.spec.ts` covers all three surfaces of this change set.

src/lib/insights/mood-aggregates.ts

@@ -979,3 +979,30 @@ export async function fetchMoodAggregates(
     })),
   };
 }
+
+/**
+ * The `/api/mood/insights` wire for one stability window.
+ *
+ * The per-window map is the cache's, not the wire's: the chosen window is
+ * served as `stability`. An aggregate cached before the map existed has only
+ * the year, so a shorter window reads as not yet computed (`null`) until the
+ * next rebuild rather than as the year's score under a new name.
+ *
+ * Shared by the route and by the `/insights/mood` server prefetch, so the
+ * cell the prefetch seeds is byte-for-byte what the client's own fetch would
+ * have put there — the same key with a different shape is silent cache poison.
+ */
+export function moodInsightsWire(
+  result: MoodAggregates,
+  stabilityWindowDays: MoodStabilityWindow,
+) {
+  const { stabilityByWindow, ...wire } = result;
+  return {
+    ...wire,
+    stability:
+      stabilityWindowDays === 365
+        ? result.stability
+        : (stabilityByWindow?.[stabilityWindowDays] ?? null),
+    stabilityWindowDays,
+  };
+}