feat(runtime): SIGHUP hot-reload of room bindings (no full restart)

Registering/deregistering a channel via a DB write from a non-main room did not
take effect until a full restart, and restarting from inside an agent turn is
unreliable (the agent is a child of ejclaw.service, so `systemctl restart` kills
it mid-command and it can't be confirmed) — the source of repeated "auto-restart
missing / claimed restart but it didn't happen" failures.

Add a SIGHUP handler that calls runtimeState.reloadRoomBindings(), which re-reads
ONLY room bindings from the DB (cursors/sessions untouched, no re-processing).
`kill -HUP <MainPID>` then makes a registration live instantly with no restart
and no agent death, so it is verifiable in the same turn.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/runtime-state.ts

@@ -20,6 +20,13 @@ import type { AgentType, RegisteredGroup } from './types.js';
 
 export interface RuntimeState {
   loadState: () => void;
+  /**
+   * Re-read ONLY the room bindings from the DB (not cursors/sessions), so a
+   * channel registered/deregistered via a DB write takes effect live without a
+   * full process restart. Safe to call at runtime — it does not touch the
+   * message cursors, so no re-processing risk.
+   */
+  reloadRoomBindings: () => void;
   saveState: () => void;
   clearSession: (groupFolder: string, opts?: { allRoles?: boolean }) => void;
   assignRoomForIpc: (jid: string, input: AssignRoomInput) => void;
@@ -96,6 +103,14 @@ export function createRuntimeState(): RuntimeState {
     );
   };
 
+  const reloadRoomBindings = (): void => {
+    roomBindings = getAllRoomBindings();
+    logger.info(
+      { groupCount: Object.keys(roomBindings).length },
+      'Room bindings reloaded',
+    );
+  };
+
   const assignRoomForIpc = (jid: string, input: AssignRoomInput): void => {
     const assignedGroup = assignRoom(jid, input);
     if (!assignedGroup) {
@@ -121,6 +136,7 @@ export function createRuntimeState(): RuntimeState {
 
   return {
     loadState,
+    reloadRoomBindings,
     saveState,
     clearSession,
     assignRoomForIpc,