feat(tasks): mark tasks and lists as manual

Reminders written down as todos had no home: every task looked like Claude work.
A manual task now shows a MANUAL badge and hides send-to-queue, refine and the
planning session; the queue picker, daily prep and the list handler all skip it,
with a TaskStateService guard so the MCP surface and hub cannot start one either.
Opening a hand-driven ConPTY session stays available on purpose.

A list can be marked manual in its settings, which makes tasks created there
(UI and MCP add_task) start out manual. Toggle per task from its context menu.

src/ClaudeDo.Worker/External/ExternalMcpService.cs

@@ -185,6 +185,8 @@ public sealed class ExternalMcpService
             CommitType = list.DefaultCommitType,
             CreatedBy = createdBy.NullIfBlank() ?? "mcp",
             Model = ModelRegistry.NormalizeAlias(model),
+            // A manual list holds reminders, so anything filed there starts out manual.
+            IsManual = list.IsManual,
         };
         await _tasks.AddAsync(entity, cancellationToken);
 
@@ -788,6 +790,8 @@ public sealed class ExternalMcpService
         var candidates = idle
             .Where(t => !t.IsMyDay
                         && t.BlockedByTaskId == null
+                        // A manual task is a reminder only the user can do — never a Claude candidate.
+                        && !t.IsManual
                         && DailyPrepFilter.IsIncludedRepo(t.List?.WorkingDir, excludes))
             .OrderBy(t => t.CreatedAt)
             .Select(ToCandidate)