fix(mcp): report a Failed task's failureReason instead of a bare status

get_task/batch_get_tasks now return failureReason (max_turns|timeout|error|
cancelled|unknown) plus failureTurnsUsed/failureMaxTurns on a Failed task, so
max_turns (worktree usually fine, continue_task) is distinguishable from a
real error (reset_failed_task) without pulling get_task_log's raw NDJSON.
Classified and stamped onto TaskEntity by TaskRunner.MarkFailed via
TaskStateService.FailAsync; TaskRunEntity also keeps the CLI's raw
terminal_reason/result_subtype/errors for deeper diagnosis. reset_failed_task's
description now warns explicitly that it discards the worktree and points at
continue_task for max_turns. Surfaced on the task card's status-chip tooltip.

src/ClaudeDo.Localization/locales/de.json

@@ -657,6 +657,8 @@
     "shell": { "restartingWorker": "Worker wird neu gestartet…", "unexpectedError": "Unerwarteter Fehler: {0}" },
     "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" },
+    "failureReason": { "maxTurns": "Turn-Limit erreicht", "timeout": "Zeitüberschreitung", "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" },
     "taskRow": { "createdPrefix": "Erstellt {0}", "stepsText": "{0}/{1} Schritte" },
     "tasksIsland": { "completedHeader": "ABGESCHLOSSEN", "completedHeaderCount": "ABGESCHLOSSEN · {0}", "planningOpenFailed": "Planungssitzung konnte nicht geöffnet werden: {0}", "planningResumeFailed": "Planungssitzung konnte nicht fortgesetzt werden: {0}", "approveFailed": "Genehmigen & Mergen fehlgeschlagen: {0}", "cancelReviewFailed": "Prüfung abbrechen fehlgeschlagen: {0}", "sendToQueueFailed": "In die Warteschlange stellen fehlgeschlagen: {0}", "queuePlanBlockedInteractive": "Plan kann nicht in die Warteschlange gestellt werden — {0} hat eine offene interaktive Sitzung und muss zuerst geschlossen werden.", "moveRunningRejected": "Ein laufender Task kann nicht in eine andere Liste verschoben werden.", "moveWorktreeRejected": "Verschieben nicht möglich — dieser Task hat einen aktiven Worktree, der auf sein aktuelles Repo zeigt.", "moveRepoConfirm": "Unterschiedliche Repos — {0} → {1}. Task trotzdem verschieben?", "moveConfirmUnavailable": "Verschieben nicht möglich — der Bestätigungsdialog ist nicht verfügbar.", "quickClaudeNoWorkingDir": "Für diese Liste ist kein Arbeitsverzeichnis konfiguriert.", "quickClaudeDirMissing": "Arbeitsverzeichnis existiert nicht mehr: {0}" },

src/ClaudeDo.Localization/locales/en.json

@@ -657,6 +657,8 @@
     "shell": { "restartingWorker": "Restarting worker…", "unexpectedError": "Unexpected error: {0}" },
     "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" },
+    "failureReason": { "maxTurns": "Turn limit reached", "timeout": "Timed out", "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" },
     "taskRow": { "createdPrefix": "Created {0}", "stepsText": "{0}/{1} steps" },
     "tasksIsland": { "completedHeader": "COMPLETED", "completedHeaderCount": "COMPLETED · {0}", "planningOpenFailed": "Couldn't open planning session: {0}", "planningResumeFailed": "Couldn't resume planning session: {0}", "approveFailed": "Approve & merge failed: {0}", "cancelReviewFailed": "Cancel review failed: {0}", "sendToQueueFailed": "Send to queue failed: {0}", "queuePlanBlockedInteractive": "Can't queue the plan — {0} has an open interactive session and must be closed first.", "moveRunningRejected": "Can't move a running task to another list.", "moveWorktreeRejected": "Can't move — this task has an active worktree pointing at its current repo.", "moveRepoConfirm": "Different repos — {0} → {1}. Move the task anyway?", "moveConfirmUnavailable": "Can't move — the confirmation dialog isn't available.", "quickClaudeNoWorkingDir": "This list has no working directory configured.", "quickClaudeDirMissing": "Working directory no longer exists: {0}" },