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/db/schema.ts

@@ -74,6 +74,7 @@ CREATE TABLE pending_questions (
 export const SESSION_SCHEMA = `
 CREATE TABLE messages_in (
   id             TEXT PRIMARY KEY,
+  seq            INTEGER UNIQUE,
   kind           TEXT NOT NULL,
   timestamp      TEXT NOT NULL,
   status         TEXT DEFAULT 'pending',
@@ -89,6 +90,7 @@ CREATE TABLE messages_in (
 
 CREATE TABLE messages_out (
   id             TEXT PRIMARY KEY,
+  seq            INTEGER UNIQUE,
   in_reply_to    TEXT,
   timestamp      TEXT NOT NULL,
   delivered      INTEGER DEFAULT 0,