feat: Add task deletion with shift+click auto-confirm

- Add deleteTask tRPC mutation (repo already had delete method)
- Add X button to TaskRow, hidden until hover, with confirmation dialog
- Shift+click bypasses confirmation for fast bulk deletion
- Invalidates listInitiativeTasks on success
- Document shift+click pattern in CLAUDE.md as standard for destructive actions

CLAUDE.md

@@ -29,6 +29,10 @@ Pre-implementation design docs are archived in `docs/archive/`.
 - **Hexagonal architecture**: Repository ports in `src/db/repositories/*.ts`, Drizzle adapters in `src/db/repositories/drizzle/*.ts`. All re-exported from `src/db/index.ts`.
 - **tRPC context**: Optional repos accessed via `require*Repository()` helpers in `src/trpc/routers/_helpers.ts`.
 
+## UI Patterns
+
+- **Shift+click to skip confirmation**: Destructive actions (delete task, etc.) show a `window.confirm()` dialog on click. Holding Shift bypasses the dialog and executes immediately. Apply this pattern to all new destructive buttons.
+
 ## Build
 
 ```sh