TASK-401: Metrics Reducer Implementation

[copyleftdev]

Description

Implement post-run metrics computation per METRICS.md

Phase

Set up development infrastructure with Tiger Style discipline

Test-First Requirements

⚠️ Write tests BEFORE implementation

• Test request count metrics
• Test latency metrics
• Test throughput calculations
• Test error rate computation
• Property test: metrics consistency with event log

Acceptance Criteria

• Read event log post-run
• Compute request metrics (total, by method, by status)
• Compute latency distribution (HDR histogram)
• Compute throughput (RPS, peak, min)
• Compute connection metrics
• Compute error metrics (total, by type)
• Assertion evaluation (pass/fail)
• Single-pass algorithm (O(N))
• Metrics computation < 3s for 10M events
• Minimum 2 assertions per function
• >95% test coverage
• Property test verified
• All tests pass

Dependencies

• TASK-400
• TASK-100

Files to Create/Modify

src/metrics.zig
tests/unit/metrics_test.zig
tests/integration/metrics_accuracy_test.zig

Estimated Effort

28 hours

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Tiger Style Requirements:

• Minimum 2 assertions per function
• All loops are bounded
• Explicit error handling (no silent failures)
• Code formatted with zig fmt
• Pre-commit hook passes
• All tests pass

[copyleftdev]

Completed in PR #96