Add task specifications for Phase 5 advanced input features

- 015-keyboard-shortcuts.md (completed)
- 020-command-palette.md (completed)
- 021-file-attachments.md (next: @mentions, drag-drop, chips)
- 022-long-paste-handling.md (summarize long pastes)
- 023-symbol-attachments.md (LSP integration)
- 024-agent-attachments.md (agent context)
- 025-image-clipboard-support.md (image handling)

tasks/todo/024-agent-attachments.md

@@ -0,0 +1,31 @@
+---
+title: Agent Attachments
+description: Allow @agent mentions for multi-agent conversations.
+---
+
+Implement Agent Attachments
+
+---
+
+### @ Agent Autocomplete
+
+When a user types `@` followed by an agent name, display an autocomplete list of available agents.
+
+Filter agent suggestions as the user types.
+
+---
+
+### Attach Agents
+
+Enable users to select an agent from the autocomplete list to attach to their prompt.
+
+Display attached agents as interactive chips.
+
+---
+
+### Acceptance Criteria
+
+- Typing `@` followed by a partial agent name displays matching agent suggestions.
+- Selecting an agent creates an attachment chip.
+- Attached agents are included in the prompt submission.
+- Agent chips can be removed.