Add a session timeline view for prompts, tool calls, permissions, and compaction events #42
Description
Summary
OAgent already renders chat messages and tool calls, but there is no dedicated timeline for understanding what happened across an entire session at an operational level. Advanced users need a higher-level event view: when prompts were sent, when tools were requested, when permissions were granted or denied, when compaction occurred, and when the runtime exited or reloaded.
Why this matters
A timeline view would improve debugging, demos, and contributor development. It would also make it easier to explain subtle bugs in state restoration, permission handling, and background-session behavior.
Acceptance Criteria
- Add a session timeline that summarizes major events in chronological order.
- Include at least: user prompts, assistant turn boundaries, tool calls, permission prompts/results, compaction events, and runtime exits/restarts.
- Events should link back to the relevant chat message or detail view when applicable.
- The timeline should remain usable for long-running sessions with many tool calls.
- The first version can be read-only, but it should be structured for future filtering or export.