ponytail-debt: scan command doesn't skip .git or node_modules

Thanks for ponytail. Reporting a small mismatch in skills/ponytail-debt/SKILL.md (v4.10.0).

The text says to skip node_modules, .git, and build output, but the command doesn't:

grep -rnE '(#|//) ?ponytail:' .

Plain recursive grep walks those directories. Markers from dependencies or generated files can end up in the ledger, and the scan is slow on large repos.

Suggested fix:

grep -rnE --exclude-dir={.git,node_modules,dist,build} '(#|//) ?ponytail:' .

Related: #810 is the same command, about block comments. One edit could cover both. Happy to open a PR if you'd like.