fix: prevent full message history from being sent to container agents

When lastAgentTimestamp was missing (new group, corrupted state, or
startup recovery), the empty-string fallback caused getMessagesSince to
return up to 200 messages — the entire group history. This sent a
massive prompt to the container agent instead of just recent messages.

Fix: recover the cursor from the last bot reply timestamp in the DB
(proof of what we already processed), and cap all prompt queries to a
configurable MAX_MESSAGES_PER_PROMPT (default 10). Covers all three
call sites: processGroupMessages, the piping path, and
recoverPendingMessages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/config.ts

@@ -53,6 +53,10 @@ export const CONTAINER_MAX_OUTPUT_SIZE = parseInt(
 ); // 10MB default
 export const ONECLI_URL =
   process.env.ONECLI_URL || envConfig.ONECLI_URL || 'http://localhost:10254';
+export const MAX_MESSAGES_PER_PROMPT = Math.max(
+  1,
+  parseInt(process.env.MAX_MESSAGES_PER_PROMPT || '10', 10) || 10,
+);
 export const IPC_POLL_INTERVAL = 1000;
 export const IDLE_TIMEOUT = parseInt(process.env.IDLE_TIMEOUT || '1800000', 10); // 30min default — how long to keep container alive after last result
 export const MAX_CONCURRENT_CONTAINERS = Math.max(