feat: password Realm, single-chair login, shared parliament context (0.9.12)

Derive Realm keys from a user password (Argon2id, no private key on disk).
Login claims the sole chair with handover; peers share parliament context;
--new-project clears it. CLI peer/discover helpers and Docker alpine recipe
included; headless empty-answer retries raised for unattended runs.

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

src/agent_loop.c

@@ -3251,11 +3251,19 @@ static int run_turn_once(cst_agent_t *a, const char *user_text,
     }
     turn_free(&t);
 
-    if (empty_retries < 2 && step + 1 < a->cfg.max_steps) {
-      empty_retries++;
-      nudge = NUDGE_EMPTY;
-      hook_status(&t, "empty response — retrying...");
-      continue;
+    /* Headless / unattended turns allow more empty-answer retries so a
+     * flaky gateway does not end the turn blank. CST_EMPTY_RETRIES overrides. */
+    {
+      int empty_cap = a->cfg.headless ? 4 : 2;
+      const char *env_er = getenv("CST_EMPTY_RETRIES");
+      if (env_er && atoi(env_er) > 0)
+        empty_cap = atoi(env_er);
+      if (empty_retries < empty_cap && step + 1 < a->cfg.max_steps) {
+        empty_retries++;
+        nudge = NUDGE_EMPTY;
+        hook_status(&t, "empty response — retrying...");
+        continue;
+      }
     }
     /* Last resort: surface the latest tool output so the turn isn't blank. */
     if (tools_ran) {