Add initial Go CLI skeleton

internal/db/schema/001_inbox.sql

@@ -0,0 +1,51 @@
+CREATE TABLE IF NOT EXISTS threads (
+  thread_id TEXT PRIMARY KEY,
+  run_id TEXT NOT NULL,
+  task_id TEXT NOT NULL,
+  subject TEXT NOT NULL,
+  created_by TEXT NOT NULL,
+  assigned_to TEXT NOT NULL,
+  status TEXT NOT NULL,
+  priority TEXT NOT NULL DEFAULT 'normal',
+  latest_message_id TEXT,
+  created_at TEXT NOT NULL,
+  updated_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS messages (
+  message_id TEXT PRIMARY KEY,
+  thread_id TEXT NOT NULL,
+  from_agent TEXT NOT NULL,
+  to_agent TEXT NOT NULL,
+  kind TEXT NOT NULL,
+  summary TEXT NOT NULL,
+  body TEXT NOT NULL DEFAULT '',
+  payload_json TEXT NOT NULL DEFAULT '{}',
+  created_at TEXT NOT NULL,
+  FOREIGN KEY(thread_id) REFERENCES threads(thread_id)
+);
+
+CREATE TABLE IF NOT EXISTS leases (
+  thread_id TEXT PRIMARY KEY,
+  agent_id TEXT NOT NULL,
+  lease_token TEXT NOT NULL,
+  claimed_at TEXT NOT NULL,
+  expires_at TEXT NOT NULL,
+  released_at TEXT
+);
+
+CREATE TABLE IF NOT EXISTS artifacts (
+  artifact_id TEXT PRIMARY KEY,
+  message_id TEXT NOT NULL,
+  path TEXT NOT NULL,
+  kind TEXT NOT NULL,
+  metadata_json TEXT NOT NULL DEFAULT '{}',
+  created_at TEXT NOT NULL,
+  FOREIGN KEY(message_id) REFERENCES messages(message_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_threads_status_assigned
+  ON threads(status, assigned_to, updated_at);
+
+CREATE INDEX IF NOT EXISTS idx_messages_thread_created
+  ON messages(thread_id, created_at);