fix: chat session reliability, cost, and hygiene (empty-response guard, tool truncation, delete, titles)

- Empty/refusal responses retried once, then surfaced as errors instead of silent blanks
- Chinese refusal boilerplate detected via denylist + non-ASCII heuristic
- Bulk-tool preference added to SOUL.md (list_lxcs over per-entity get_lxc_state)
- Tool results truncated to 4KB on persist; get_state_snapshot filters null-state entities
- Session delete (DELETE /sessions/{id} + confirm-on-second-click UI)
- Session titles auto-generated from assistant answer instead of raw user message

internal/mcp/server.go

@@ -698,6 +698,8 @@ func newServer(pool *db.Pool, agentID uuid.UUID) *mcp.Server {
 			       COALESCE(st.last_check_at::text, '') AS last_check
 			FROM entities e
 			LEFT JOIN entity_status st ON st.entity_id = e.id
+			WHERE e.state IS NOT NULL
+			   OR st.health IS NOT NULL
 			ORDER BY st.health, e.slug
 			LIMIT 200
 		`), nil