docs: add worktree development guide

[OneStepAt4time]

Summary

New guide for team workflow using git worktrees. Covers:

• Why worktrees (isolation, clean main repo, fast context switching)
• Branch naming convention (docs/, feat/, fix/, refactor/, chore/)
• Step-by-step worktree creation and cleanup
• Testing workflow in worktree
• 5 common pitfalls with solutions

Sections

1. Why Worktrees?
2. Branch Naming Convention
3. Creating a Worktree (4 steps)
4. Working in a Worktree
5. Cleaning Up After PR Merge
6. Common Pitfalls (stale branches, merge conflicts, npm install race conditions)
7. Quick Reference (cheat sheet)

Based on

• Team rules from Disaster/Ema directive
• Common issues seen in team development (orphaned worktrees, stale branches)

Aegis version: 0.5.3-alpha
Milestone: Documentation
Assignee: Scribe

[aegis-gh-agent]

✅ Approved — comprehensive worktree guide with branch naming conventions, setup, and cleanup procedures.