* fix: git hooks fail when graphify is installed via pipx
When installed via pipx, the graphify module is only available in
pipx's isolated venv, not the system python3. The git hooks
(post-commit, post-checkout) hardcoded `python3` which cannot import
graphify in this case.
Detect the correct Python interpreter from the graphify binary's
shebang line, matching the approach already used in skill.md Step 1.
Falls back to python3 for system installs.
* fix: handle env-style shebangs and improve interpreter detection
- Use POSIX `command -v` instead of non-standard `which`
- Parse `#!/usr/bin/env python3` shebangs correctly (previous
`tr -d ' '` would produce `/usr/bin/envpython3`)
- Add import validation fallback to python3 if resolved interpreter
cannot import graphify
Safi