fix: use atomic counter in pet-pipenv test temp dirs to prevent parallel collisions

[karthiknadig]

The unique_temp_dir() helper in pet-pipenv tests used SystemTime::now().as_nanos() to generate temp directory names. On Windows, SystemTime has ~15.6ms resolution, so parallel test threads can get the same value — causing one test's cleanup (remove_dir_all) to destroy another test's files mid-execution.

Fix: Replace the nanos-based name with process_id + AtomicU64 counter, which is guaranteed unique across parallel test threads within the same test binary.

This was observed as a flaky detect_pipenv_centralized_env_without_project_file_via_naming_pattern failure on Windows CI (e.g., PR #407 CI run).

[github-actions]

Test Coverage Report (Linux)

Metric	Value
Current Coverage	73.2%
Base Branch Coverage	73.2%
Delta	0% ➖

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Coverage unchanged.

[github-actions]

Performance Report (Linux) ➖

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	1ms	2ms	1ms	0ms	0%
Full Refresh	97ms	543ms	79ms	18ms	20.0%

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

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Legend

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

[github-actions]

Performance Report (macOS)

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta
Server Startup	77ms	612ms	61ms	16ms
Full Refresh	149ms	33162ms	118ms	31ms

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]

Performance Report (Windows) ➖

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	11ms	16ms	9ms	2ms	22.2%
Full Refresh	185ms	649ms	154ms	31ms	20.1%

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	69.4%
Base Branch Coverage	69.41%
Delta	-0.01% ❌

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Coverage decreased. Please add tests for new code.