Add comprehensive documentation about beads-created worktrees:
- New section in WORKTREES.md explaining why and where beads creates worktrees
- Common confusion: 'beads took over main!' with solution
- Troubleshooting entries for 'branch already checked out' errors
- FAQ entry: 'Why did beads create worktrees in my .git directory?'
This addresses user confusion when beads' sync-branch feature creates
internal worktrees that can lock branches users want to checkout.
Closes#510🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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