Resolve python tools off PATH, not just as importable modules

1.1.0 reported an installed ruff as missing and skipped the lint. Its
resolution order ended at `python -m <tool>`, guarded by an `import <tool>`
probe, but ruff ships as a standalone Rust binary and is never importable.
The probe failed, the check was recorded as skipped, and the gate reported a
coverage gap that did not exist.

This also regressed 1.0.2, which called a bare `ruff` and let PATH resolve it.
Restore that path, ordered after the project venv and uv so a project-local
tool still wins, and before `python -m` so a binary is found even when a
same-named module is not importable.

Verified by injecting an unused import into audit-terraform and confirming the
guard blocks with `ruff check .`. The new regression test fails against the
1.1.0 resolution order and passes against this one.

Tests: 10 passing (bash-guard), 197 (audit-code), 106 (audit-terraform),
ruff clean across both skills.

plugins/guards/hooks/test-bash-guard.py

@@ -96,4 +96,11 @@ with tempfile.TemporaryDirectory() as tmp:
     r = run_guard(bash("jj git push --bookmark main"), cwd=tmp)
     check("passing nested test allows the push", decision(r) != "deny", f"got {decision(r)!r}")
 
+with tempfile.TemporaryDirectory() as tmp:
+    skill = nested_repo(tmp, "def test_passes():\n    assert True\n")
+    open(os.path.join(skill, "scripts.py"), "w").write("import os\n")
+    r = run_guard(bash("jj git push --bookmark main"), cwd=tmp)
+    check("lint failure blocks the push", decision(r) == "deny", f"got {decision(r)!r}")
+    check("ruff is resolved off PATH, not skipped", "ruff" in reason(r), f"got {reason(r)!r}")
+
 sys.exit(1 if failures else 0)