v2 phase 4+5: Discord via Chat SDK, expanded MCP tools, message seq IDs

- Chat SDK bridge + Discord adapter (gateway listener, message routing)
- MCP tools refactored into modular structure: core (send_message, send_file,
  edit_message, add_reaction), scheduling (schedule/list/cancel/pause/resume
  tasks), interactive (ask_user_question, send_card), agents (send_to_agent)
- Message seq IDs: shared integer sequence across messages_in/out so agents
  see small numeric IDs instead of platform snowflakes
- busy_timeout=5000 for session DB (poll loop + MCP server concurrent access)
- Always copy agent-runner source to fix stale cache when non-index files change
- Seed script for Discord testing, e2e test script

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

src/session-manager.ts

@@ -108,11 +108,23 @@ export function writeSessionMessage(
   db.pragma('journal_mode = DELETE');
 
   try {
+    const nextSeq = (
+      db
+        .prepare(
+          `SELECT COALESCE(MAX(seq), 0) + 1 AS next FROM (
+             SELECT seq FROM messages_in WHERE seq IS NOT NULL
+             UNION ALL
+             SELECT seq FROM messages_out WHERE seq IS NOT NULL
+           )`,
+        )
+        .get() as { next: number }
+    ).next;
     db.prepare(
-      `INSERT INTO messages_in (id, kind, timestamp, status, platform_id, channel_type, thread_id, content, process_after, recurrence)
-       VALUES (@id, @kind, @timestamp, 'pending', @platformId, @channelType, @threadId, @content, @processAfter, @recurrence)`,
+      `INSERT INTO messages_in (id, seq, kind, timestamp, status, platform_id, channel_type, thread_id, content, process_after, recurrence)
+       VALUES (@id, @seq, @kind, @timestamp, 'pending', @platformId, @channelType, @threadId, @content, @processAfter, @recurrence)`,
     ).run({
       id: message.id,
+      seq: nextSeq,
       kind: message.kind,
       timestamp: message.timestamp,
       platformId: message.platformId ?? null,