fix: validate executable filename before spawning in resolve_environment (Fixes #364)

[karthiknadig]

Adds validation in resolve_environment() to check that the executable filename matches a Python executable pattern before proceeding with the locator chain or spawning. Previously, any file (e.g., Jupyter kernel spec bash wrapper scripts) would be spawned with -c "import sys;...", wasting ~13 seconds and executing arbitrary non-Python executables.

• Made is_python_executable_name() public in pet-python-utils to reuse existing regex patterns
• Added early return with warn! log in resolve_environment() when filename doesn't match

Fixes #364

[github-actions]

Performance Report (Linux) ✅

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	1ms	1ms	1ms	0ms	0%
Full Refresh	97ms	520ms	98ms	-1ms	0%

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

---

Legend

• 🚀 Significant speedup (>100ms faster)
• ✅ Faster than baseline
• ➖ No significant change
• 🔺 Slower than baseline (>100ms)
• ⚠️ Significant slowdown (>500ms)

[github-actions]

Test Coverage Report (Linux)

Metric	Value
Current Coverage	62.7%
Base Branch Coverage	62.7%
Delta	0% ➖

---

Coverage unchanged.

[github-actions]

Performance Report (Windows) ✅

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	10ms	13ms	10ms	0ms	0%
Full Refresh	163ms	613ms	181ms	-18ms	-9.9%

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

---

Legend

• 🚀 Significant speedup (>100ms faster)
• ✅ Faster than baseline
• ➖ No significant change
• 🔺 Slower than baseline (>100ms)
• ⚠️ Significant slowdown (>500ms)

[github-actions]

Test Coverage Report (Windows)

Metric	Value
Current Coverage	58.89%
Base Branch Coverage	58.89%
Delta	0% ➖

---

Coverage unchanged.

[Copilot]

Pull request overview

This PR adds filename validation to prevent spawning non-Python executables in the resolve_environment() function, fixing issue #364 where Jupyter kernel spec helper scripts were being executed with Python arguments, causing ~13 second delays and confusing error logs.

Changes:

• Made is_python_executable_name() function public in pet-python-utils to enable validation of executable filenames
• Added early validation check in resolve_environment() to reject files that don't match Python executable naming patterns (python, python3, python3.11, etc.) before attempting to spawn them

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
crates/pet-python-utils/src/executable.rs	Made is_python_executable_name() function public to allow reuse for validation
crates/pet/src/resolve.rs	Added import of is_python_executable_name and early validation check to reject non-Python executables before spawning

Comments suppressed due to low confidence (1)

crates/pet/src/resolve.rs:63

• Consider adding a test case to verify that non-Python executables (like bash scripts) are properly rejected by resolve_environment. This would help prevent regression of the fix for issue #364. The test could create a temporary non-Python file and verify that resolve_environment returns None with an appropriate warning.

    if executable.is_file() && !is_python_executable_name(&executable) {
        warn!(
            "Path {:?} does not look like a Python executable, skipping resolve",
            executable
        );
        return None;
    }

[github-actions]

Performance Report (macOS)

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta
Server Startup	54ms	512ms	63ms	-9ms
Full Refresh	105ms	26319ms	138ms	-33ms

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

---

Legend

• 🚀 Significant speedup (>100ms faster)
• ✅ Faster than baseline
• ➖ No significant change
• 🔺 Slower than baseline (>100ms)
• ⚠️ Significant slowdown (>500ms)