fix(worker): allow the done toggle from any non-Running status

MarkDoneAsync was Idle-only, so a finished task (typically a list-handler
run with no worktree to merge) could not be ticked off. Guard on Running
instead and cover the other statuses with tests.

src/ClaudeDo.Worker/CLAUDE.md

@@ -70,7 +70,7 @@ not conflated.
 Allowed transitions (enforced by `TaskStateService`):
 
 ```
-Idle               → Queued | Running (RunNow) | Done (manual toggle) | Cancelled (external update_task_status only, allowFromIdle: true)
+Idle               → Queued | Running (RunNow) | Cancelled (external update_task_status only, allowFromIdle: true)
 Queued             → Running | Cancelled | Idle | Failed (OverrideSlotService preflight gap)
 Running            → WaitingForReview (standalone success, no children)
                    | WaitingForChildren (parent with pending children)
@@ -80,8 +80,14 @@ WaitingForReview   → Done (approve) | Queued (reject-rerun, +feedback) | Idle
 Done               → Idle (re-run)
 Failed             → Idle | Queued
 Cancelled          → Idle | Queued
+
+any except Running → Done (manual done toggle, SetTaskDone)
 ```
 
+The manual done toggle is the one cross-cutting transition — it ticks a task off from **any**
+status except `Running`, skipping the merge on purpose (a worktree-less list-handler task has
+nothing to merge; a worktree task's branch just stays Active for the worktrees overview).
+
 **Unified parent model.** Every parent — planning *or* improvement — flows
 `… → WaitingForChildren → WaitingForReview → Done` via the single `TryAdvanceParentAsync`.
 Planning/improvement **children** go straight to `Done`; only the parent is reviewed.

src/ClaudeDo.Worker/State/TaskStateService.cs

@@ -382,14 +382,19 @@ public sealed class TaskStateService : ITaskStateService
     public async Task<TransitionResult> MarkDoneAsync(string taskId, DateTime finishedAt, CancellationToken ct)
     {
         await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
+        // The done toggle is a manual "tick it off" affordance and works from every status
+        // except Running (a live run keeps writing the row, so the picker/runner would race).
+        // WaitingForReview is deliberately included: ticking a finished task done skips the
+        // merge on purpose -- for a worktree-less list-handler task there is nothing to merge,
+        // and for a worktree task the branch just stays Active for the worktrees overview.
         var affected = await ctx.Tasks
-            .Where(t => t.Id == taskId && t.Status == TaskStatus.Idle)
+            .Where(t => t.Id == taskId && t.Status != TaskStatus.Running)
             .ExecuteUpdateAsync(s => s
                 .SetProperty(t => t.Status, TaskStatus.Done)
                 .SetProperty(t => t.FinishedAt, finishedAt), ct);
 
         if (affected == 0)
-            return new TransitionResult(false, "Task is not Idle; cannot mark done.");
+            return new TransitionResult(false, "Task is running or no longer exists; cannot mark done.");
 
         await _broadcaster.TaskUpdated(taskId);
         return new TransitionResult(true, null);