feat: parliament seat collaboration loop (0.9.19)

Seats publish via parliament_note, sync pushes on write, member join without
stealing the chair, and worker tools are hard-gated when parliament is active.

Co-authored-by: Cursor <cursoragent@cursor.com>

include/cst_parliament.h

@@ -31,26 +31,47 @@ int cst_parliament_save(const cst_parliament_meta_t *m);
 char *cst_parliament_login(const char *password, const char *instance_id,
                            const char *device_label, char *err, size_t err_sz);
 
+/* Join as a peer seat without stealing the chair (claims only if vacant).
+ * Returns JOIN_OK summary (malloc'd) or NULL. */
+char *cst_parliament_seat_join(const char *password, const char *instance_id,
+                               const char *device_label, char *err,
+                               size_t err_sz);
+
 /* Only one chair: previous chair is demoted; handover notes left in meta. */
 int cst_parliament_claim_chair(const char *instance_id, const char *device_label);
 
 /* Probe local environment as device-private context (malloc'd text). */
 char *cst_parliament_device_context(void);
 
+/* Prefer CST_INSTANCE_ID, else sanitized hostname (never empty). */
+int cst_parliament_default_instance(char *out, size_t n);
+
 /* New project: wipe shared parliament context; keep Realm keys. */
 int cst_parliament_new_project(const char *project_id);
 
 /* Resolve collaboration mode: env CST_COLLABORATION, then settings,
  * then password-Realm with an open parliament → "parliament". */
 int cst_parliament_is_active(void);
+/* 1 when the local seat ticket matches the current chair. */
+int cst_parliament_is_chair(void);
 /* Short status lines for TUI/CLI (malloc'd; caller frees). */
 char *cst_parliament_status_text(void);
 
 /* Append/replace synchronized context blob (all agents share this file). */
 int cst_parliament_context_put(const char *text);
 char *cst_parliament_context_get(void);
+/* Append a structured seat note and bump revision (triggers peer sync).
+ * kind: status | agenda | result | handover | note */
+int cst_parliament_context_append(const char *seat_id, const char *kind,
+                                  const char *body);
 
-/* Local login ticket: opens require a fresh chair session (or password env). */
+/* Ask the local parliament service to dial peers soon (best-effort). */
+void cst_parliament_sync_request(void);
+int cst_parliament_sync_pending(void);
+void cst_parliament_sync_ack(void);
+
+/* Local login ticket: opens require a fresh seat session (or password env).
+ * Any enrolled seat may hold a ticket; chair is tracked separately in meta. */
 int cst_parliament_session_write(const char *instance_id);
 int cst_parliament_session_ok(char *instance_id_out, size_t n);
 void cst_parliament_session_clear(void);