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>

src/tools/registry.c

@@ -10,6 +10,7 @@
 
 #include "cJSON.h"
 #include "cst_clipboard.h"
+#include "cst_parliament.h"
 #include "cst_runtime.h"
 #include "cst_tools.h"
 #include "cst_util.h"
@@ -166,6 +167,15 @@ static const cst_tool_def_t TOOLS[] = {
      NULL,
      {{"todos", S, 1, "the whole list, one item per line"}},
      CST_TP_META, 0, cst_tool_todo_write, NULL, NO_DYN, NO_META},
+    {"parliament_note",
+     "Publish a short note into the shared parliament context so other seats "
+     "see progress (synced over the sealed peer channel). Use after finishing "
+     "a block of cross-seat work, when posting agenda, or when handing over. "
+     "kind: status | agenda | result | handover | note.",
+     NULL,
+     {{"note", S, 1, "short note body for other seats"},
+      {"kind", S, 0, "status|agenda|result|handover|note (default status)"}},
+     CST_TP_META, 0, cst_tool_parliament_note, NULL, NO_DYN, NO_META},
     {"web_search",
      "Search the live web through the current Kimi or DeepSeek provider and "
      "return titles, URLs and snippets. Use web_fetch to read a result.",
@@ -580,6 +590,15 @@ int cst_tool_active(const cst_agent_config_t *cfg, const cst_tool_def_t *t) {
     return 0;
   if (cfg->depth > 0 && (!strcmp(t->owner ? t->owner : "", "builtin:runtime") ||
       !strncmp(t->name, "worker_", 7))) return 0;
+  /* Parliament seats coordinate via sealed peer sync, not in-process workers. */
+  if (cst_parliament_is_active()) {
+    if (!strcmp(t->name, "task") || !strncmp(t->name, "worker_", 7))
+      return 0;
+    if (t->owner && !strcmp(t->owner, "builtin:runtime"))
+      return 0;
+  } else if (!strcmp(t->name, "parliament_note")) {
+    return 0;
+  }
   if (cfg->tools_only[0]) {
     char key[CTL_MAX_NAME + 2];
     snprintf(key, sizeof(key), ",%s,", t->name);