fix(worker): make external MCP filter params optional, surface tool errors

Nullable filter/patch params across the External/ MCP tool classes (ListTasks,
UpdateTask, AddSubtask, ReviewTask, SetMyDay, SetListConfig/SetTaskConfig,
CreateList/UpdateList) lacked C# default values, so the generated tool schema
marked them required — MCP clients omitting them (the common case) failed.
Gave every such parameter a default value.

Also registered a call-tool filter (ExternalMcpExceptionFilter) on the external
MCP host that translates InvalidOperationException/ArgumentException into
McpException, since the SDK's own catch-all discards ex.Message for any other
exception type and returns a generic "An error occurred invoking 'X'." string.

Added a reflection-based schema test sweeping every [McpServerToolType] class
to guard against reintroducing a required-but-nullable parameter.

src/ClaudeDo.Worker/CLAUDE.md

@@ -32,7 +32,7 @@ Interfaces (e.g. `IQueueWaker`, `IPrimeClock`, `ITaskStateService`) live in an `
 - **IQueueWaker / IQueuePicker / QueueService** — waker is a singleton `SemaphoreSlim`; picker performs the atomic `Queued → Running` claim filtered by `BlockedByTaskId IS NULL` and schedule; QueueService is a thin `BackgroundService` that loops on the waker and dispatches via `TaskRunner`.
 - **OverrideSlotService** — owns `RunNow` / `ContinueTask`; goes through `TaskStateService.StartRunningAsync` (caller-driven, serialized by slot lock).
 - **StaleTaskRecovery** — startup-only service; calls `TaskStateService.RecoverStaleRunningAsync` to flip orphaned `Running` rows to `Failed`.
-- **External/*** — always-on MCP tools for general Claude sessions, scoped to *starting* and *observing* sessions (no worktree/merge, multi-turn, planning, or app-settings writes). Auth via optional `X-ClaudeDo-Key` header. Registered explicitly in `Program.cs`'s external app via `.WithTools<T>()`. Organized by concern:
+- **External/*** — always-on MCP tools for general Claude sessions, scoped to *starting* and *observing* sessions (no worktree/merge, multi-turn, planning, or app-settings writes). Auth via optional `X-ClaudeDo-Key` header. Registered explicitly in `Program.cs`'s external app via `.WithTools<T>()`. Every optional/filter parameter across these tools must carry a C# default value (e.g. `string? status = null`) — the MCP schema only marks a parameter optional when it has one; nullability alone doesn't do it (`ExternalMcpToolSchemaTests` guards this by reflection). `ExternalMcpExceptionFilter.Wrap` is registered as a call-tool filter so `InvalidOperationException`/`ArgumentException` messages survive as `McpException` — otherwise the SDK's own catch-all replaces any non-`McpException` with a generic "An error occurred invoking 'X'." Organized by concern:
   - `ExternalMcpService` — task CRUD + execution: `ListTaskLists`, `ListTasks`, `GetTask`, `AddTask`, `AddSubtask`, `UpdateTask`, `UpdateTaskStatus` (`Idle` / `Queued`), `GetTaskStatusValues`, `ReviewTask` (`approve` / `reject_rerun` / `reject_park` / `cancel` for a WaitingForReview task), `RunTaskNow`, `ContinueTask`, `CancelTask`, `DeleteTask`; worktree/git: `GetTaskWorktree`, `GetTaskDiff`, `MergeTask`, `ListWorktrees`, `CleanupTaskWorktree`
   - `BatchMcpTools` — best-effort batch variants that loop the `ExternalMcpService` single-entity methods (sequential — the scoped DbContext is not thread-safe; merge/review stay single-task): `BatchGetTasks`, `BatchAddTasks`, `BatchUpdateTaskStatus`, `BatchCancelTasks`, `BatchDeleteTasks`, `BatchSetMyDay`, `BatchCleanupTaskWorktrees`. Every tool returns a per-item result array ({ id/index, ok, error?, … }) — a failing item never aborts the rest — and rejects batches over 100 items.
   - `ListMcpTools` — `CreateList`, `UpdateList`, `DeleteList`