fix: exclude VCS metadata directories from copy-ignored

[worktrunk-bot]

Summary

• wt step copy-ignored now skips VCS metadata directories (.jj, .hg, .svn, .sl, .bzr, .pijul) that are colocated with git
• These directories contain internal state tied to a specific working directory — copying them between worktrees breaks the colocated VCS (e.g., Jujutsu re-adds hidden files after seeing a stale .jj directory)
• Git's own .git is implicitly excluded (never reported by git ls-files), but other colocated VCS tools need explicit exclusion

Closes #1249

Test plan

• New integration test test_copy_ignored_skips_vcs_metadata_dirs verifies .jj and .hg are excluded while regular ignored files (.env) are still copied
• All 33 existing copy-ignored tests pass unchanged
• Clippy clean
• Doc sync passes (step.md and skill reference updated automatically)

🤖 Generated with Claude Code

[max-sixty]

is there any distinction between .git/info/exclude and ignore? I'm less familiar with this difference.

[worktrunk-bot]

They're both sources of ignore patterns that --exclude-standard combines, but scoped differently:

• .gitignore — tracked in the repo, shared with collaborators. The common one (node_modules/, target/, etc.)
• .git/info/exclude — local to the repo, not tracked/shared. For patterns you want to ignore personally without putting them in .gitignore
• Global excludes (core.excludesFile) — user-wide, applies to all repos (e.g. .DS_Store)

In practice, .git/info/exclude is where someone running e.g. jj colocated might put .jj/ to keep it out of git status without modifying the shared .gitignore. All three feed into the same git ls-files --ignored --exclude-standard call, so copy-ignored sees them identically — the distinction is just about where the pattern lives.

That said, this doc line predates this PR — I can simplify it to just say "Handles all gitignore sources (.gitignore, global excludes, .git/info/exclude)" or similar if you'd prefer a clearer phrasing.