docs(attachments): document task file attachments across project docs

Data/Worker/Ui CLAUDE.md + docs/open.md updated for TaskAttachmentEntity,
AttachmentStore, AttachmentMcpTools, AttachmentOrphanRecovery, the run-prompt
injection, and the detail-pane drag-and-drop UI (incl. a manual verification
item).

src/ClaudeDo.Worker/CLAUDE.md

@@ -8,7 +8,7 @@ ASP.NET Core hosted service that executes tasks via Claude CLI in isolated envir
 Worker/
   State/        — TaskStateService + TransitionResult (sole owner of Status/PlanningPhase/BlockedBy writes)
   Queue/        — IQueueWaker, IQueuePicker, QueueService (BackgroundService), OverrideSlotService
-  Lifecycle/    — StaleTaskRecovery, TaskResetService, TaskMergeService, ClaudeCliPreflight, OrphanRecovery, PlanningLineageRecovery
+  Lifecycle/    — StaleTaskRecovery, TaskResetService, TaskMergeService, ClaudeCliPreflight, OrphanRecovery, PlanningLineageRecovery, AttachmentOrphanRecovery (startup sweep: deletes any `attachments/<taskId>/` dirs whose task no longer exists)
   Worktrees/    — WorktreeMaintenanceService
   Agents/       — AgentFileService, DefaultAgentSeeder
   Runner/       — TaskRunner + Claude CLI integration; TaskRunMcpService/TaskRunMcpContext/TaskRunTokenRegistry (in-task MCP wired during execution)
@@ -39,6 +39,7 @@ Interfaces (e.g. `IQueueWaker`, `IPrimeClock`, `ITaskStateService`) live in an `
   - `AgentMcpTools` — `ListAgents` (class lives in `LifecycleMcpTools.cs`)
   - `LifecycleMcpTools` — `ResetFailedTask`
   - `AppSettingsMcpTools` — `GetAppSettings` (read-only)
+  - `AttachmentMcpTools` — `AddTaskAttachment(taskId, fileName, textContent?|base64Content?)`, `ListTaskAttachments`, `RemoveTaskAttachment`. Re-attaching the same fileName overwrites; add/remove refuse on a Running task.
   - `ExternalMcpService` also exposes two daily-prep tools:
     - `GetDailyPrepCandidates` — returns Idle, non-blocked tasks in a git repo NOT excluded by `AppSettings.ReportExcludedPaths` and not already `IsMyDay`, plus the current Idle MyDay tasks and `maxTasks` (= `DailyPrepMaxTasks`). Repo-exclusion logic lives in the `DailyPrepFilter` helper (same file).
     - `SetMyDay` — sets a task's `IsMyDay` (+ optional `SortOrder`); server-side cap-guard rejects turning on MyDay beyond `DailyPrepMaxTasks` open (Idle) MyDay tasks.
@@ -118,7 +119,7 @@ A child that hits a roadblock (fails, or reports `CLAUDEDO_BLOCKED` roadblocks)
 1. Load task + list metadata from DB; resolve config from `list_config` + task-level overrides (model, system_prompt, agent_path)
 2. Create worktree (if `WorkingDir` set) or sandbox directory
 3. Mark task "running", broadcast `TaskStarted`
-4. Build CLI args via `ClaudeArgsBuilder`; invoke `ClaudeProcess` with task prompt
+4. Build CLI args via `ClaudeArgsBuilder`; inject attachment absolute paths via `TaskPromptComposer.Compose` (appends a read-only "## Reference files" section); invoke `ClaudeProcess` with task prompt
 5. Stream NDJSON output through `StreamAnalyzer`; lines forwarded to log file and SignalR (`TaskMessage`)
 6. On success: auto-commit changes (worktree only), store run record, mark "done"
 7. On failure: retry once if session ID available (`--resume`), then mark "failed"