mom: turn-based context, timestamp fixes, system prompt improvements (#68)

Breaking Changes:
- Timestamps now use Slack format - run migrate-timestamps.ts for existing logs

Added:
- Channel/user ID mappings in system prompt
- Skills documentation in system prompt
- Debug last_prompt.txt output
- Bash working directory info
- Token-efficient log queries filtering tool calls

Changed:
- Turn-based message context (groups consecutive bot messages as one turn)
- Messages sorted by Slack timestamp
- Condensed system prompt (~5k → ~2.7k chars)
- Simplified user prompt
- Selective logging (skip UI status labels)

Fixed:
- Duplicate message logging from app_mention handler
- Username obfuscation in thread messages

packages/mom/src/log.ts

@@ -160,6 +160,10 @@ export function logStopRequest(ctx: LogContext): void {
 }
 
 // System
+export function logInfo(message: string): void {
+	console.log(chalk.blue(`${timestamp()} [system] ${message}`));
+}
+
 export function logWarning(message: string, details?: string): void {
 	console.log(chalk.yellow(`${timestamp()} [system] ⚠ ${message}`));
 	if (details) {