Add PreCompact hook for conversation archiving, remove /clear command

- Add PreCompact hook in agent-runner that archives conversations before
  compaction, using session summary from sessions-index.json for filename
- Remove /clear command (programmatic compaction not supported by SDK)
- Add /add-clear to RFS for future implementation
- Update CLAUDE.md templates with memory system instructions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/skills/customize/SKILL.md

@@ -73,7 +73,7 @@ Questions to ask:
 
 Implementation:
 1. Add command handling in `processMessage()` in `src/index.ts`
-2. Follow the pattern used for `/clear`
+2. Check for the command before the trigger pattern check
 
 ### Changing Deployment