chore: add .claude/rules/ scoped rules and CLAUDE.md compact instructions

[cmbays]

Context

Adopting scoped rules (.claude/rules/ with paths: frontmatter) across all repos for better context management during Claude Code sessions. Rules load on-demand when matching files are touched, keeping context clean and signal density high.

Based on context engineering research — see ops repo for the pattern.

What to do

1. Update .gitignore to track .claude/rules/ (use .claude/* + !.claude/rules/ pattern)
2. Create .claude/rules/ with scoped rules for this repo's domains (e.g., workflow engine, skills, DAG execution)
3. Add to CLAUDE.md (create or update):
   • Rule Maintenance section — instruct Claude to auto-update rules when new patterns/risks are discovered
   • Compact Instructions section — what to preserve/discard during compaction

Reference

• Ops pattern: ops/.claude/rules/ (standards-authoring, research, vision-and-prd, vault-content, playbooks)
• Mokumo pattern: mokumo/.claude/rules/ (domain-model, api-and-infrastructure, frontend, testing)

Rules should be scoped to this repo's specific file structure and conventions.