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/en.json

@@ -239,6 +239,7 @@
     "toggleSubtasksTip": "Expand / collapse subtasks",
     "agentSuggestedTip": "Suggested by the agent",
     "interactiveChipTip": "Interactive session open — click to jump to it in Mission Control",
+    "waitingOnTip": "Waiting on {0}",
     "scheduleTitle": "Schedule task",
     "scheduleWhen": "WHEN",
     "scheduleConfirm": "Schedule",
@@ -277,6 +278,7 @@
     "starTip": "Star",
     "agentSettingsTip": "Agent settings",
     "agentSettingsHeading": "Agent settings (overrides)",
+    "waitingOnPrefix": "Waiting on",
     "copyFormattedTip": "Copy title, description and open steps",
     "toggleEditPreviewTip": "Toggle edit/preview",
     "planDay": "Plan day",
@@ -775,7 +777,7 @@
     "shell": { "restartingWorker": "Restarting worker…", "unexpectedError": "Unexpected error: {0}" },
     "mainWindow": { "closeConfirm": { "message": "{0} Mission Control session(s) are still running. Closing the app will end them. Close anyway?" } },
     "agentStatus": { "idle": "Idle", "queued": "Queued", "running": "Running", "review": "Review", "children": "Waiting for Subtasks", "done": "Done", "failed": "Failed", "cancelled": "Cancelled" },
-    "taskStatus": { "idle": "Idle", "queued": "Queued", "running": "Running", "waitingForReview": "Waiting for Review", "waitingForChildren": "Waiting for Subtasks", "done": "Done", "failed": "Failed", "cancelled": "Cancelled", "parked": "Parked", "interactive": "Interactive" },
+    "taskStatus": { "idle": "Idle", "queued": "Queued", "running": "Running", "waitingForReview": "Waiting for Review", "waitingForChildren": "Waiting for Subtasks", "done": "Done", "failed": "Failed", "cancelled": "Cancelled", "parked": "Parked", "interactive": "Interactive", "waiting": "Waiting" },
     "failureReason": { "maxTurns": "Turn limit reached", "timeout": "Timed out", "usageLimit": "Usage limit reached", "error": "Error", "cancelled": "Cancelled", "unknown": "Unknown reason" },
     "failureReasonTooltip": { "maxTurns": "Turn limit reached ({0}/{1} turns) — the worktree is usually fine; continue the task instead of resetting it." },
     "planningBadge": { "active": "PLANNING", "finalized": "PLANNED" },