feat: add task management CLI and improve activity curation

- Add task store with dependency tracking and CLI (packages/server/src/tasks/)
- Extract principal param logic to shared util for server/app reuse
- Improve activity curator: collapse timeline, dedupe tool calls, simpler output
- Add MessageInput ref for focus control after agent cancel
- Include recent activity in wait timeout messages

🤖 Generated with [Claude Code](https://claude.com/claude-code)

.tasks/0c32789c.md

@@ -0,0 +1,9 @@
+---
+id: 0c32789c
+title: Add three random numbers
+status: open
+deps: [2769910f, 7018be3f, 537563b5]
+created: 2026-01-07T16:32:47.905Z
+---
+
+Epic: We will add three random numbers together. Task 1 picks a number, Task 2 adds another, Task 3 adds a third and reports the final sum.