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.Data/CLAUDE.md

@@ -12,6 +12,7 @@ Shared data layer: models, repositories, SQLite infrastructure, and git operatio
 - **PrimeScheduleEntity** — Id, Days (`[Flags] PrimeDays` weekday bitmask, stored as `days_of_week` int), TimeOfDay, Enabled, LastRunAt, PromptOverride, CreatedAt. Recurs on the selected weekdays; no date range.
 - **DailyNoteEntity** — Id, Date (DateOnly), Text, SortOrder, CreatedAt → table `daily_notes`
 - **WeekReportEntity** — Id, StartDate/EndDate (DateOnly), Markdown, GeneratedAt → table `week_reports`, unique index on (start_date, end_date)
+- **TaskAttachmentEntity** — Id, TaskId (FK to tasks, ON DELETE CASCADE), FileName, ByteSize, CreatedAt → table `task_attachments`
 - **AppSettingsEntity** also carries `ReportExcludedPaths` (string?, JSON array of excluded path prefixes, column `report_excluded_paths`), `StandupWeekday` (int DayOfWeek, default Wednesday, column `standup_weekday`), and `DailyPrepMaxTasks` (int, default 5, column `daily_prep_max_tasks` — hard cap on how many open tasks the daily-prep / "Prime Claude" feature may place in MyDay)
 - **SubtaskEntity**, **AppSettingsEntity**, **AgentInfo** — existing helpers / settings / record for scanned agent files
 
@@ -25,6 +26,7 @@ All repositories use EF Core LINQ queries via `ClaudeDoDbContext`. The atomic `Q
 - **TaskRunRepository**, **SubtaskRepository**, **AppSettingsRepository**
 - **DailyNoteRepository** — `ListByDayAsync`, `ListBetweenAsync`, `AddAsync`, `UpdateAsync`, `DeleteAsync`
 - **WeekReportRepository** — `GetByRangeAsync`, `UpsertAsync`
+- **TaskAttachmentRepository** — `AddAsync`, `UpdateAsync`, `GetAsync(taskId, fileName)`, `ListByTaskIdAsync`, `DeleteAsync(taskId, fileName)`, `DeleteAllForTaskAsync`
 
 ## Infrastructure
 
@@ -32,6 +34,7 @@ All repositories use EF Core LINQ queries via `ClaudeDoDbContext`. The atomic `Q
 - **IDbContextFactory<ClaudeDoDbContext>** — registered in DI; used by singleton consumers (e.g. Worker hosted service)
 - **Paths** — expands `~` and `%USERPROFILE%`, resolves relative paths. App root: `~/.todo-app`
 - **AppSettings** — loads `~/.todo-app/ui.config.json` (DbPath, SignalRUrl)
+- **AttachmentStore** — dependency-free file store; default root `~/.todo-app/attachments/<taskId>/`. `SaveAsync` enforces a 5 MB cap and path-traversal/containment guard. Also exposes `DeleteFile`, `DeleteTaskDir`, `TaskDir`, `Root`, and `EnumerateTaskIds` (used by the worker orphan sweep). Attachment files live outside git worktrees intentionally.
 
 ## Git
 
@@ -39,7 +42,7 @@ All repositories use EF Core LINQ queries via `ClaudeDoDbContext`. The atomic `Q
 
 ## Schema
 
-Tables: `lists`, `tasks`, `worktrees`, `list_config`, `task_runs`, `subtasks`, `app_settings`, `prime_schedules`, `daily_notes`, `week_reports`. Managed by EF Core migrations in the `Migrations/` folder. The `tasks` table holds `status`, `planning_phase` (default `none`), and `blocked_by_task_id` (FK to `tasks.id`, `ON DELETE SET NULL`). Migration `WeeklyReport` added `daily_notes`, `week_reports`, and the two new `app_settings` columns. Migration `DailyPrepMaxTasks` added the `daily_prep_max_tasks` column to `app_settings` (no new tables).
+Tables: `lists`, `tasks`, `worktrees`, `list_config`, `task_runs`, `subtasks`, `app_settings`, `prime_schedules`, `daily_notes`, `week_reports`, `task_attachments`. Managed by EF Core migrations in the `Migrations/` folder. The `tasks` table holds `status`, `planning_phase` (default `none`), and `blocked_by_task_id` (FK to `tasks.id`, `ON DELETE SET NULL`). Migration `WeeklyReport` added `daily_notes`, `week_reports`, and the two new `app_settings` columns. Migration `DailyPrepMaxTasks` added the `daily_prep_max_tasks` column to `app_settings` (no new tables). Migration `AddTaskAttachments` created the `task_attachments` table. `TaskRepository.DeleteAsync` and `ListRepository.DeleteAsync` also delete the on-disk attachment dir(s) via an optional `AttachmentStore` ctor param (defaults to the production store).
 
 ## Conventions