feat(voyage): add lib/exporters/textfile-format.mjs — Prometheus text-format pure transform SC #12
Step 9 av v4.1-execute (Wave 2, Session 3).
Pure function transformToPrometheus(records) → Prometheus text-format 0.0.4.
Hard rules:
- NO client-side timestamps (research/01 node_exporter#1284 mitigation)
- Allowlist-redacted records ONLY (caller responsibility — Step 11 enforces)
- UTF-8 metric names normalized: lowercase, [.\\-\\s] → _, voyage_ prefix
- Empty input → empty string output
- Sorted output for determinism (snapshot-test-friendly)
Heuristic metric typing:
- counter: *_total, *_count, *_passed, *_failed, *_skipped
- histogram: *_ms, *_duration, *_p\\d+, *_seconds
- gauge: everything else (Prometheus convention)
Snapshot: tests/fixtures/expected.prom byte-for-byte match.
Regenerate: node scripts/gen-expected-prom.mjs > tests/fixtures/expected.prom
Tester (6 nye, baseline 400 → 406):
- Snapshot byte-for-byte match (SC #12)
- Empty input handling (null, undefined, [])
- Allowlist-redaction sanity (post-bash-stats uten command_excerpt)
- NO client-side timestamps (token-count-assertion per linje)
- normalizeMetricName edge-cases
- Determinism (identisk input → identisk output)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Kjell Tore Guttormsen
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