Escape regex metacharacters in ASSISTANT_NAME for trigger pattern (#16)

ASSISTANT_NAME was interpolated directly into a regex without escaping.
If the name contained regex metacharacters (e.g., @A.*), the trigger
would match unintended patterns. This adds escapeRegex() to properly
escape special characters before building the TRIGGER_PATTERN.

https://claude.ai/code/session_01Lvuxq73qa9S4rtmGpX1WsP

Co-authored-by: Claude <noreply@anthropic.com>

src/config.ts

@@ -19,7 +19,11 @@ export const CONTAINER_IMAGE = process.env.CONTAINER_IMAGE || 'nanoclaw-agent:la
 export const CONTAINER_TIMEOUT = parseInt(process.env.CONTAINER_TIMEOUT || '300000', 10);
 export const IPC_POLL_INTERVAL = 1000;
 
-export const TRIGGER_PATTERN = new RegExp(`^@${ASSISTANT_NAME}\\b`, 'i');
+function escapeRegex(str: string): string {
+  return str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+}
+
+export const TRIGGER_PATTERN = new RegExp(`^@${escapeRegex(ASSISTANT_NAME)}\\b`, 'i');
 
 // Timezone for scheduled tasks (cron expressions, etc.)
 // Uses system timezone by default