perf(status): batch git process spawning in status command

[kaihowl]

Replace N+1 sequential git calls with 2 git calls regardless of how many
commits have pending measurements:

• Add get_commits_with_notes_content() that runs git notes list followed
  by a single git log --no-walk --notes= to fetch commit metadata and
  note content together in one pass.
• Update gather_pending_status() to use the new batch function, eliminating
  the per-commit get_notes_for_commit() and get_commit_details() calls.
• Remove now-dead get_notes_for_commit() and get_commit_details() functions.

Closes #608

https://claude.ai/code/session_01Gf2dy3haEC63m3f3qC4zYG

[github-actions]

Performance Report

⏱ Performance Results

Audit Results

Auditing measurement "add-benchmark" (os=ubuntu-22.04/rust=beta):
  ⏭️ 'add-benchmark'
  Only 1 historical measurement found. Less than requested min_measurements of 10. Skipping test.
  Aggregation: min
  z-score (mad): ↓
  Head: μ: 15.5ms σ: N/A MAD: 0ns n: 1
  Tail: μ: 20.1ms σ: N/A MAD: 0ns n: 1
   [-22.79% – +0.00%] █▁

Auditing measurement "add-benchmark" (os=ubuntu-22.04/rust=stable):
  ⏭️ 'add-benchmark'
  Only 1 historical measurement found. Less than requested min_measurements of 10. Skipping test.
  Aggregation: min
  z-score (mad): ↑
  Head: μ: 20.3ms σ: N/A MAD: 0ns n: 1
  Tail: μ: 14.5ms σ: N/A MAD: 0ns n: 1
   [+0.00% – +39.96%] ▁█

Auditing measurement "release-binary-size" (os=ubuntu-22.04/rust=stable):
  ✅ 'release-binary-size'
  Aggregation: min
  z-score (stddev): ↑ 1.24
  Head: μ: 8.1MB σ: N/A MAD: 0B n: 1
  Tail: μ: 8MB σ: 45.9kB MAD: 38.5kB n: 35
   [-1.57% – +1.16%] ▇▇█▆▆▆▆▆▆▆▆▆▆▆▅▅▅▅▅▅▅▅▅▅▅▅▄▄▄▄▄▁███▇

Auditing measurement "report" (os=ubuntu-22.04/rust=beta):
  ✅ 'report'
  Aggregation: min
  z-score (stddev): ↓ 1.31
  Head: μ: 19.2ms σ: N/A MAD: 0ns n: 1
  Tail: μ: 22.8ms σ: 2.7ms MAD: 299.6µs n: 36
   [-28.11% – +6.29%] ▇▇▇▇▇▆█▂▂▇▇▇▆▂▂▇▇▇▇▆▁▂█▆▁▇▂▇▇▇▇▆▇▇▇▂▃

Auditing measurement "report" (os=ubuntu-22.04/rust=stable):
  ✅ 'report'
  Aggregation: min
  z-score (stddev): ↑ 0.29
  Head: μ: 24.6ms σ: N/A MAD: 0ns n: 1
  Tail: μ: 23.9ms σ: 2.2ms MAD: 356.8µs n: 36
   [-29.22% – +8.43%] ▁▆▆▂▆▆▂█▇▁▇▇▇▆▆▆▆▇▇▆▆▆▇▇▇▆▇█▆▇▇▆▆▆▇▆▇

Auditing measurement "report-benchmark" (os=ubuntu-22.04/rust=beta):
  ⏭️ 'report-benchmark'
  Only 1 historical measurement found. Less than requested min_measurements of 10. Skipping test.
  Aggregation: min
  z-score (stddev): ↓
  Head: μ: 18.9ms σ: N/A MAD: 0ns n: 1
  Tail: μ: 24.5ms σ: N/A MAD: 0ns n: 1
   [-22.87% – +0.00%] █▁

Auditing measurement "report-benchmark" (os=ubuntu-22.04/rust=stable):
  ⏭️ 'report-benchmark'
  Only 1 historical measurement found. Less than requested min_measurements of 10. Skipping test.
  Aggregation: min
  z-score (stddev): ↑
  Head: μ: 25.1ms σ: N/A MAD: 0ns n: 1
  Tail: μ: 17.9ms σ: N/A MAD: 0ns n: 1
   [+0.00% – +40.05%] ▁█

Auditing measurement "report-size" (os=ubuntu-22.04/rust=beta):
  ✅ 'report-size'
  Aggregation: min
  z-score (stddev): ↑ 1.67
  Head: μ: 20.3kB σ: N/A MAD: 0B n: 1
  Tail: μ: 15.3kB σ: 3kB MAD: 2.9kB n: 36
   [-18.78% – +31.30%] ████████▄▄▄▄▄▄▄▄▄▄▄▄▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█

Auditing measurement "report-size" (os=ubuntu-22.04/rust=stable):
  ✅ 'report-size'
  Aggregation: min
  z-score (stddev): ↑ 1.67
  Head: μ: 20.3kB σ: N/A MAD: 0B n: 1
  Tail: μ: 15.3kB σ: 3kB MAD: 2.9kB n: 36
   [-18.78% – +31.30%] ████████▄▄▄▄▄▄▄▄▄▄▄▄▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█

Auditing measurement "report-size-benchmark" (os=ubuntu-22.04/rust=beta):
  ⏭️ 'report-size-benchmark'
  Only 8 historical measurements found. Less than requested min_measurements of 10. Skipping test.
  Aggregation: median
  z-score (stddev): →
  Head: μ: 20.3kB σ: N/A MAD: 0B n: 1
  Tail: μ: 20.3kB σ: 0B MAD: 0B n: 8
   [+0.00% – +0.00%] ▅▅▅▅▅▅▅▅▅

Auditing measurement "report-size-benchmark" (os=ubuntu-22.04/rust=stable):
  ⏭️ 'report-size-benchmark'
  Only 8 historical measurements found. Less than requested min_measurements of 10. Skipping test.
  Aggregation: median
  z-score (stddev): →
  Head: μ: 20.3kB σ: N/A MAD: 0B n: 1
  Tail: μ: 20.3kB σ: 0B MAD: 0B n: 8
   [+0.00% – +0.00%] ▅▅▅▅▅▅▅▅▅

Overall: PASSED (11/11 groups passed)

Measurement Storage Size

Live Measurement Size Report
============================

⚠️  Shallow clone detected - measurement counts may be incomplete (see FAQ)

Number of commits with measurements: 312
Total measurement data size (on-disk (compressed)): 417.4kB

Repository Statistics (for context):
-------------------------------------
  Loose objects: 0 (0B)
  Packed objects: 11997 (2.8MB)
  Total repository size: 2.8MB

Created by git-perf

[github-actions]

🧬 PR Mutation Testing Results

Status: ✅ All mutants caught - excellent test coverage!

Mutation Testing Metrics (Changed Code Only)

Metric	Count
Total Mutants	5
✅ Caught	3
❌ Missed	0
⏱️ Timeout	0
🚫 Unviable	2

Mutation Score: 100.0% (3/3 viable mutants caught)

✅ Great Job!

All mutants in your changes were caught by the test suite. Your code is well-tested!

---

Incremental mutation testing only tests code modified in this PR.
Full mutation testing runs weekly to catch issues in unchanged code.

📦 Artifacts

Download full mutation report