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

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.tasks/537563b5.md

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+---
+id: 537563b5
+title: Add third random number and report final sum
+status: done
+deps: [7018be3f]
+created: 2026-01-07T16:32:57.495Z
+---
+
+Pick a final random number between 1-100. Read previous notes to get the running total. Add your number. Record in notes: 'Added: X, FINAL SUM: Y'
+
+## Notes
+
+**2026-01-07T16:34:56.240Z**
+
+Added: 42, FINAL SUM: 112