feat(06-06): distinct all-day event pill styling

- Add .sx__all-day-event override to Schedule-X section of index.css
- Full-width rounded pill: border-radius 4px, white (#FFFFFF) label, font-weight 600,
  font-size var(--text-label-size) — UI-SPEC Surface 3 contract
- Color source: calendarId color config (buildCalendarConfig) — no per-event override
- Timed event chip styling unchanged; existing .sx__* layout rules intact

apps/pwa/src/styles/index.css

@@ -53,3 +53,26 @@ body {
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
 }
+
+/* ── Schedule-X overrides ──────────────────────────────────────────────────── */
+
+/*
+ * 999.6 / D-12: All-day event visual distinction.
+ *
+ * All-day events render as full-width filled rounded pills so they are immediately
+ * distinct from timed event chips (partial-fill with colored left border accent).
+ *
+ * Contract (Surface 3 — UI-SPEC):
+ *   all-day = solid filled pill  → this override
+ *   timed   = partial-fill chip with colored border accent (Schedule-X default)
+ *
+ * Color source: the member's `_familySync.color` propagates via `calendarId` color
+ * config in buildCalendarConfig() — no per-event inline override needed.
+ * Override selector confirmed from @schedule-x/theme-default@4.6.0.
+ */
+.sx__all-day-event {
+  border-radius: 4px;
+  color: #FFFFFF;
+  font-weight: 600;
+  font-size: var(--text-label-size);
+}