fix(FN-827): fix orphaned pause path so gracefully-paused tasks return to todo

- Fix executor bug where tasks paused during execution with a graceful session exit were silently dropped instead of moved back to todo
- When session.dispose() resolves the prompt without throwing, the paused-aborted flag now triggers moveTask(todo) so the scheduler can resume after unpause
- Add executor test suite covering pause via graceful exit, pause via abort error, and pause during session disposal
- Document corrected pause/unpause behavior for in-progress tasks in README and AGENTS.md

.changeset/fix-orphaned-pause-path.md

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+"@gsxdsm/fusion": patch
+---
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+Fix orphaned pause path: gracefully-paused tasks now correctly move back to todo