fix: replace unbounded additions ratio with bounded net additions ratio

[kenjudy]

The previous formula (additions / max(deletions, 1)) inflated ratios to ~500 for net-new-file commits, distorting both median and p90. The RETROSPECTIVE documented p90=446x as dominated by this artifact.

New formula: (additions - deletions) / (additions + deletions), bounded [-1, +1]. Value 1.0 = entirely net-new code; 0.0 = balanced; negative = net cleanup. Equivalent threshold: old 3.0 → new 0.50 (mathematically derived: when additions = 3×deletions, (3d-d)/(3d+d) = 0.50).

Changes:

• local-code-metrics.js: replace ratio formula, rename summary fields additions_ratio_* → net_additions_ratio_*
• .github/workflows/code-metrics.yml: same formula fix and field rename, update issue body threshold display, clean up redundant sort+map
• .github/workflows/pr-metrics.yml: fix || 1 bug in deletions variable, rename per-commit field, update median ratio threshold and display
• metrics-specification.md: rewrite Metric 7 with new formula, bounded range explanation, remapped thresholds, rejection rationale
• tests/collectLocalMetrics.test.js: add regression test asserting median ≤ 1.0 for all-new-file commits; update field name assertions

[github-actions]

PR Analysis

Size: small (based on production code)
Production Code: 92 lines (5 files)
Test Code: 38 lines (1 files)
Total: 130 lines (6 files)
Test-to-Production Ratio: 0.41:1

Concerns

• 1/1 commits touch more than 5 files

Strengths

• Strong test-first discipline across commits
• Message quality 100% meets discipline threshold

Commit Analysis

Total Commits: 1
Average Commit Size: 92 production lines
Average Files per Commit: 6.0

Metric	Value
Large commits (>100 prod lines)	0/1 (0%)
Sprawling commits (>5 files)	1/1 (100%)
Test-first discipline	1/1 (100%)
Message quality	1/1 (100%)
Median net additions ratio	0.49
Test-only commits	0
Production-only commits	0

Commit Details

e8b0d14 Ken Judy (4/7/2026)
fix: replace unbounded additions ratio with bounded net additions ratio
92 prod lines, 6 files [sprawling, test+prod]

Test Coverage

Test Adequacy: good

• Good balance of production and test code

Target ratio: 0.5-2.0 test lines per production line

DORA Capability Assessment

Archetype: mixed-signals
No clear archetype pattern. Review individual metric thresholds.

Capability	Metric	Value	Target
Small Batches	Large commit %	0%	<20%
Small Batches	Sprawling commit %	100%	<10%
Version Control	Test-first discipline	100%	>50%
Version Control	Message quality	100%	>60%
AI Risk Signal	Net additions ratio (median)	0.49	<0.50
Automated by Code Metrics Workflow