feat(ui): surface depends_on blocking in status chip, chain label, and detail pane

Usability-Audit 2026-09-10 found three gaps versus the dependency-chain-display
spec: a Queued task blocked on an unmet task_dependencies edge rendered the same
chip as one about to run, a cross-list predecessor silently dropped the
"after #N" chip, and the detail pane showed nothing about a wait at all.

- TaskRowViewModel gains IsBlockedByDependency/DependencyWaitLabel (extrinsic,
  assigned by TasksIslandViewModel like the existing chain fields); IsQueued/
  IsWaiting/StatusChipClass/StatusLabel/StatusChipTooltip now account for it
  alongside the existing BlockedByTaskId planning-chain link.
- TasksIslandViewModel.ApplyDependencyWaitState computes the blocked flag and
  wait label per row; a new RefreshExternalDependencyCacheAsync backfills
  Number/Title/Status for predecessors not loaded into the current list's
  Items (reusing the already-open DbContext, no new hub method), so
  BuildAfterLabel/blocking both resolve a listenfremder Vorgänger correctly.
- New "waiting" chip style (IslandStyles.axaml) and locale keys (en+de);
  TaskHeaderBar shows a "Waiting on #N" line bound straight to the same row.

Tests: TasksIslandChainTests (blocked/unblocked chip, cross-list predecessor),
DetailsIslandDependencyWaitTests (new), TaskRowViewModelNotificationsTests
updated for the new notification set.

src/ClaudeDo.Localization/locales/de.json

@@ -239,6 +239,7 @@
     "toggleSubtasksTip": "Unteraufgaben ein-/ausklappen",
     "agentSuggestedTip": "Vom Agenten vorgeschlagen",
     "interactiveChipTip": "Interaktive Sitzung offen — klicken, um im Mission Control dorthin zu springen",
+    "waitingOnTip": "Wartet auf {0}",
     "scheduleTitle": "Aufgabe planen",
     "scheduleWhen": "WANN",
     "scheduleConfirm": "Planen",
@@ -277,6 +278,7 @@
     "starTip": "Favorit",
     "agentSettingsTip": "Agent-Einstellungen",
     "agentSettingsHeading": "Agent-Einstellungen (Überschreibungen)",
+    "waitingOnPrefix": "Wartet auf",
     "copyFormattedTip": "Titel, Beschreibung und offene Schritte kopieren",
     "toggleEditPreviewTip": "Bearbeiten/Vorschau umschalten",
     "planDay": "Tag planen",
@@ -775,7 +777,7 @@
     "shell": { "restartingWorker": "Worker wird neu gestartet…", "unexpectedError": "Unerwarteter Fehler: {0}" },
     "mainWindow": { "closeConfirm": { "message": "{0} Mission-Control-Sitzung(en) laufen noch. Beim Beenden werden sie abgebrochen. Trotzdem schließen?" } },
     "agentStatus": { "idle": "Leerlauf", "queued": "In Warteschlange", "running": "Läuft", "review": "Prüfung", "children": "Wartet auf Teilaufgaben", "done": "Fertig", "failed": "Fehlgeschlagen", "cancelled": "Abgebrochen" },
-    "taskStatus": { "idle": "Leerlauf", "queued": "In Warteschlange", "running": "Läuft", "waitingForReview": "Wartet auf Prüfung", "waitingForChildren": "Wartet auf Teilaufgaben", "done": "Fertig", "failed": "Fehlgeschlagen", "cancelled": "Abgebrochen", "parked": "Geparkt", "interactive": "Interaktiv" },
+    "taskStatus": { "idle": "Leerlauf", "queued": "In Warteschlange", "running": "Läuft", "waitingForReview": "Wartet auf Prüfung", "waitingForChildren": "Wartet auf Teilaufgaben", "done": "Fertig", "failed": "Fehlgeschlagen", "cancelled": "Abgebrochen", "parked": "Geparkt", "interactive": "Interaktiv", "waiting": "Wartet" },
     "failureReason": { "maxTurns": "Turn-Limit erreicht", "timeout": "Zeitüberschreitung", "usageLimit": "Nutzungslimit erreicht", "error": "Fehler", "cancelled": "Abgebrochen", "unknown": "Grund unbekannt" },
     "failureReasonTooltip": { "maxTurns": "Turn-Limit erreicht ({0}/{1} Turns) — der Worktree ist meist brauchbar; Task fortsetzen statt zurücksetzen." },
     "planningBadge": { "active": "PLANUNG", "finalized": "GEPLANT" },