Add PreCompact hook for transcript backup

[ikuwow]

Summary

• Add a PreCompact hook that backs up the full transcript JSONL to ~/.claude/transcript-backups/ before compaction
• Record the backup file path in the project's memory directory (compact-snapshot.md) so Claude can find it on demand
• Fires on both manual (/compact) and automatic compaction

Motivation

When Claude Code compacts the conversation, detailed context (code snippets, error messages, step-by-step reasoning) is lost. This hook preserves the full transcript so it can be referenced later (e.g., during /retrospective).

Test plan

• Run ./scripts/deploy.sh and verify symlink for pre_compact_backup.py
• Run /compact in a Claude Code session
• Verify backup file appears in ~/.claude/transcript-backups/
• Verify compact-snapshot.md is created in the project's memory directory

🤖 Generated with Claude Code