Add data source connectors — GitHub, Slack, file system watcher #62

Problem

Memory only comes from agent hooks and API. There are no pre-built connectors for common data sources. Leading memory platforms offer 30+ connectors.

Proposed Solution

Start with 3 high-value connectors:

1. GitHub connector: Sync repo issues, PRs, discussions as memories
2. Slack/Discord connector: Capture team knowledge from conversations
3. File system watcher: Automatic memory from file changes in watched directories

Impact

Enables memory accumulation from sources beyond just agent hook events.