feat: add seq cursor, work_items, provider fallback, and delivery reliability

Major reliability improvements to the message processing pipeline:

- Add messages.seq monotonic cursor replacing timestamp-based cursors,
  preventing message loss from timestamp collisions with LIMIT queries
- Add work_items table separating agent production from delivery,
  enabling delivery retry without re-running the agent
- Propagate Discord send failures instead of silently swallowing them
- Add Claude 429 → Kimi K2.5 automatic provider fallback with cooldown
- Fix follow-up turn state reset in live index.ts path (not just
  message-runtime.ts) to prevent final output from being lost
- Add restart context tracking for graceful restart announcements
- Lazy migration from timestamp cursors to seq cursors for existing data

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/restart-context-cli.ts

@@ -0,0 +1,70 @@
+import { SERVICE_ID } from './config.js';
+import { writeRestartContext } from './restart-context.js';
+
+function printUsageAndExit(): never {
+  console.error(
+    [
+      'Usage:',
+      '  tsx src/restart-context-cli.ts write --chat-jid <jid> --summary <text> [--verify <text> ...] [--service-id <id> ...]',
+    ].join('\n'),
+  );
+  process.exit(1);
+}
+
+const [, , command, ...args] = process.argv;
+if (command !== 'write') {
+  printUsageAndExit();
+}
+
+let chatJid = '';
+let summary = '';
+const verify: string[] = [];
+const serviceIds: string[] = [];
+
+for (let i = 0; i < args.length; i += 1) {
+  const arg = args[i];
+  const value = args[i + 1];
+  if (!value) {
+    printUsageAndExit();
+  }
+
+  if (arg === '--chat-jid' || arg === '--jid') {
+    chatJid = value;
+    i += 1;
+    continue;
+  }
+  if (arg === '--summary') {
+    summary = value;
+    i += 1;
+    continue;
+  }
+  if (arg === '--verify') {
+    verify.push(value);
+    i += 1;
+    continue;
+  }
+  if (arg === '--service-id') {
+    serviceIds.push(value);
+    i += 1;
+    continue;
+  }
+
+  printUsageAndExit();
+}
+
+if (!chatJid || !summary) {
+  printUsageAndExit();
+}
+
+const written = writeRestartContext(
+  {
+    chatJid,
+    summary,
+    verify,
+  },
+  serviceIds.length > 0 ? serviceIds : [SERVICE_ID],
+);
+
+for (const filePath of written) {
+  console.log(filePath);
+}