## Why
Resuming a conversation that is open in another app fails with an active-writer error. Allow users to inspect its transcript and retry after closing it in the other app.
## What changed
- Fall back to a read-only history snapshot on active-writer conflicts during startup and session selection.
- Replace the composer with an explanatory notice, `R` to retry, exit shortcuts, and the configured transcript shortcut.
- Block input and freeze active command and MCP animations while viewing the snapshot. Preserve initial prompts and existing drafts for a successful retry.
- Keep the subscription when retrying the same thread and preserve read-only state across thread switches and reconnects.
## Testing
Add regression tests for conflict detection, history viewing, draft preservation, same-thread retry without unsubscribing, exit shortcuts, and notice and frozen-tool rendering.
GitOrigin-RevId: fa864cc73143cad9139c22e33b7958569eec20cf
4aec23384e