feat(hooks): base new worktrees on next

[blafourcade]

🎯 What & why

New worktrees created by Claude Code branched from the repo default (origin/HEAD = main). Day-to-day work targets next, so worktrees should start there. This adds a WorktreeCreate hook that bases every new worktree on next, falling back to main when next is absent.

🛠️ How it works

Claude Code's WorktreeCreate hook replaces the default git worktree add: it reads { name } on stdin and must print the created worktree path on stdout.

.claude/hooks/worktree-create.js does exactly that — picks next (else main), then git worktree add <root>/.claude/worktrees/<name> -b worktree-<name> <base>, and prints the path. git's own output goes to stderr so stdout stays the path only. .claude/settings.json registers it.

Kept deliberately minimal: only .name is documented as hook input, so no speculative field parsing. Base is the local next branch (not origin/next) to keep it simple; call out if fresh-from-origin is wanted.

🧪 How to verify

• claude --worktree probe from repo root
• git -C .claude/worktrees/probe log --oneline -1 → matches next tip
• git -C .claude/worktrees/probe branch --show-current → worktree-probe

⚠️ Heads-up

Not yet exercised by a real claude --worktree run — logic tested only in throwaway repos. The .name input key is from docs, not observed live; if the worktree lands empty, the payload key differs and the script needs adjusting.

✅ I certify

• I DO CERTIFY I READ EACH LINE OF THE PULL REQUEST BECAUSE I AM A SOFTWARE ENGINEER, NOT A AI PUPPY.