Fix three regressions introduced by PR #18370 (lazy session creation):
1. _finalize_session() uses stale session_key after compression (#20001)
2. session_key not synced after auto-compression in run_conversation (#20001)
3. pending_title ValueError leaves title wedged forever (#19029)
4. Gateway silently swallows null responses when agent did work (#18765)
5. One-time cleanup for accumulated ghost compression continuations (#20001)
Changes:
- tui_gateway/server.py: _finalize_session() now uses agent.session_id
(falls back to session_key when agent is None). Refactor
_sync_session_key_after_compress() with clear_pending_title and
restart_slash_worker policy flags. Call it post-run_conversation()
to sync session_key after auto-compression. Add ValueError handler
to pending_title flush.
- gateway/run.py: Extract _normalize_empty_agent_response() helper that
consolidates failed/partial/null response handling. Surfaces user-facing
error when agent did work (api_calls > 0) but returned no text.
- hermes_state.py: Add finalize_orphaned_compression_sessions() — marks
ghost continuation sessions as ended (non-destructive, preserves data).
- cli.py: One-time startup migration for orphaned compression sessions.
Test changes:
- tests/test_tui_gateway_server.py: Update pending_title ValueError test
for post-#18370 architecture (title applied post-message, not at create).
- tests/test_lazy_session_regressions.py: 14 new regression tests covering
all fixed paths.
