Update source code and remove runtime data from tracking

Add gitignore rules for browser session data, SQLite databases,
media downloads, and build artifacts. Remove previously tracked
runtime files from the repository.

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

src/database/client.ts

@@ -81,6 +81,12 @@ export function runMigrations(db: Database.Database): void {
   db.exec(`CREATE INDEX IF NOT EXISTS idx_sent_messages_response ON sent_messages(got_response)`);
   db.exec(`CREATE INDEX IF NOT EXISTS idx_sent_messages_recipient ON sent_messages(recipient)`);
 
+  // Add strategy_id column for A/B testing
+  addColumnIfNotExists('sent_messages', 'strategy_id', 'TEXT');
+
+  // Add subreddit column to successful_messages for smarter example selection
+  addColumnIfNotExists('successful_messages', 'subreddit', 'TEXT');
+
   // Migration: Make sent_message_id nullable in successful_messages
   // SQLite doesn't support ALTER COLUMN, so we need to recreate the table
   const successfulMsgColumns = db.prepare(`PRAGMA table_info(successful_messages)`).all() as { name: string; notnull: number }[];