mom: add working memory system and improve log querying

- Add MEMORY.md files for persistent working memory
  - Global memory: workspace/MEMORY.md (shared across channels)
  - Channel memory: workspace/<channel>/MEMORY.md (channel-specific)
  - Automatically loaded into system prompt on each request

- Enhance JSONL log format with ISO 8601 dates
  - Add 'date' field for easy grepping (e.g., grep '"date":"2025-11-26"')
  - Migrated existing logs to include date field

- Improve log query efficiency
  - Add jq query patterns to prevent context overflow
  - Emphasize limiting NUMBER of messages (10-50), not truncating text
  - Show full message text and attachments in queries
  - Handle null/empty attachments with (.attachments // [])

- Optimize system prompt
  - Add current date/time for date-aware operations
  - Format recent messages as TSV (43% token savings vs raw JSONL)
  - Add efficient query examples with both JSON and TSV output

- Enhanced security documentation
  - Add prompt injection risk warnings
  - Document credential exfiltration scenarios
  - Provide mitigation strategies

packages/mom/src/store.ts

@@ -8,7 +8,8 @@ export interface Attachment {
 }
 
 export interface LoggedMessage {
-	ts: string; // slack timestamp
+	date: string; // ISO 8601 date (e.g., "2025-11-26T10:44:00.000Z") for easy grepping
+	ts: string; // slack timestamp or epoch ms
 	user: string; // user ID (or "bot" for bot responses)
 	userName?: string; // handle (e.g., "mario")
 	displayName?: string; // display name (e.g., "Mario Zechner")
@@ -104,6 +105,21 @@ export class ChannelStore {
 	 */
 	async logMessage(channelId: string, message: LoggedMessage): Promise<void> {
 		const logPath = join(this.getChannelDir(channelId), "log.jsonl");
+
+		// Ensure message has a date field
+		if (!message.date) {
+			// Parse timestamp to get date
+			let date: Date;
+			if (message.ts.includes(".")) {
+				// Slack timestamp format (1234567890.123456)
+				date = new Date(parseFloat(message.ts) * 1000);
+			} else {
+				// Epoch milliseconds
+				date = new Date(parseInt(message.ts, 10));
+			}
+			message.date = date.toISOString();
+		}
+
 		const line = JSON.stringify(message) + "\n";
 		await appendFile(logPath, line, "utf-8");
 	}
@@ -113,6 +129,7 @@ export class ChannelStore {
 	 */
 	async logBotResponse(channelId: string, text: string, ts: string): Promise<void> {
 		await this.logMessage(channelId, {
+			date: new Date().toISOString(),
 			ts,
 			user: "bot",
 			text,