feat(knowledge): review and revoke agent memory — user control over learned knowledge

[teyrebaz33]

Closes #1156

Summary

Implements full user control over everything the agent has learned, including memory entries, skills, and session history.

Changes

1. Provenance Tracking

• Memory entries now store [saved:TIMESTAMP|session:SESSION_ID] metadata prefix
• Skills get a <- Full suite: 3220 passed, 0 failed ( 1 pre-existing failure unrelated to this PR installed:TIMESTAMP|source:IDENTIFIER --> comment in SKILL.md on install
• Backward compatible: legacy entries without metadata still work

2. hermes memory CLI Command

• hermes memory list — show all memory entries with timestamp and session provenance
• hermes memory delete <text> — delete entry by content substring
• hermes memory clear — clear all memory entries
• hermes memory forget-session <id> — remove all entries saved during a session

3. hermes knowledge CLI Command

• hermes knowledge show — unified view of memory, skills, and recent sessions
• hermes knowledge forget-session <id> — bulk delete all knowledge from a session (memory entries + session DB record)

4. TTL (Auto-expiry)

• memory.ttl_days config option — entries older than N days are removed on load
• Legacy entries without timestamp are kept regardless of TTL

5. Approval Mode

• memory.approval_mode: true config option
• When enabled, add() returns pending_approval: true instead of saving
• Agent must call add(..., approved=True) after getting user confirmation

Config

memory:
  ttl_days: 30        # Auto-expire entries after 30 days (null = never)
  approval_mode: true # Require user confirmation before saving memory

Testing

• 22 new tests covering provenance, TTL, approval mode, CLI commands
• All existing memory tool tests updated for backward compatibility
• 287 passed, 0 failed