fix(using-git-worktrees): default to global worktree location to avoid CLAUDE.md double-loading

[stablegenius49]

Problem

Project-local worktrees (.worktrees/ inside the repo) can cause nested worktrees to load both the worktree's CLAUDE.md and the parent repo's CLAUDE.md, creating conflicting instructions.

Closes #279

Solution

• Default to global worktree location: ~/.config/superpowers/worktrees/<project-name>/
• Reuse existing conventions when present (both global and project-local)
• Only ask user if they need project-local after recommending global
• Update quick reference, example workflow, and best practices to reflect new default

Changes

• Updated "Directory Selection Process" to prioritize global location by default
• Updated Quick Reference table with new priority order
• Updated Example Workflow to use global location
• Added note in Overview about avoiding CLAUDE.md double-loading

Testing

• No automated tests for skill documentation (manual verification)
• Diff is documentation-only, reversible

Checklist

• Diff is small and reversible
• No risky/destructive operations
• Respects contribution rules (documentation improvement)

[mvanhorn]

Summary

Clean change - defaulting to global worktree location to avoid CLAUDE.md double-loading makes sense. The priority reordering (CLAUDE.md > existing > global default > ask) is logical.

Findings

The existing ### For Global Directory safety section (line 88-90) is a one-liner: "No .gitignore verification needed - outside project entirely." Now that global is the default path, it might be worth expanding this in a follow-up to mention git worktree prune for cleaning stale refs - if a user deletes the global directory manually instead of using git worktree remove, the next git worktree add to the same path would fail with "already registered as a worktree."

One small inline suggestion on the Quick Reference table to mirror the "(verify ignored)" safety note the project-local rows have.

Recommendation

Looks good to merge. The suggestion is a minor improvement, not a blocker.

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Review assisted by Claude Code

[mvanhorn]

Consider adding a safety note parallel to the project-local rows' "(verify ignored)". If the user previously deleted the global worktree directory without git worktree remove, stale refs in .git/worktrees/ would cause git worktree add to fail.

Suggested change

	| Global worktree dir exists | Reuse global location |
	| Global worktree dir exists | Reuse global location (prune stale refs) |