feat+test+docs: D49 — lib/audit-query.mjs (Phase 3 audit aggregate query layer) (#26)

Second Phase 3 D-day. Implements ADR 0008 § 4 query API. Pure in-memory
ndjson scan; cross-file walk over audit.ndjson (live) +
audit-YYYY-MM-DD.ndjson (rotated). No server.mjs integration in this
D-day (D50 wires the consuming endpoints).

NEW lib/audit-query.mjs (~370 lines): 5 public API functions per
ADR 0008 § 4.1:

  - discoverAuditFiles({ olpHome }): filesystem scan; returns
    Map<date|'live', path>.
  - readAuditWindow({ startMs, endMs, olpHome, logEvent }): generator
    over events in half-open window [startMs, endMs). Walks rotated
    date files + live file. Skips malformed lines + logs warn.
  - aggregateRequests({ windowMs, olpHome }): counts + status buckets
    + by_provider + by_owner_tier + by_path + median/p95 latency over
    rolling window.
  - topFallbackChains({ windowMs, limit, olpHome }): top-N chains by
    trigger count from events with fallback_hops > 0. Tied-count
    tiebreak: ascending first_seen.
  - spendTrendDaily({ days, olpHome }): daily series ending today
    with sparse-fill for zero-request days. Per-day request_count +
    median latency + by_provider breakdown.
  - cacheHitRateWindow({ windowMs, olpHome }): audit-derived cache
    hit rate (bypass excluded from denominator); per-provider + overall.

PII discipline (ADR 0008 § 4.3): every aggregate function relays only
schema fields; never message content. Suite 23g actively asserts the
absence of content/message/messages/prompt/response/body keys in every
aggregate output.

Cross-file walk semantics (ADR 0008 § 4.2): half-open window
[startMs, endMs); date-range computed once from window bounds; each
rotated date file checked; live audit.ndjson always checked (it
covers today regardless of whether the window endpoint is past
midnight).

spendTrendDaily calendar-date semantics:
  days: N returns "last N calendar UTC dates ending today" — NOT
  "events within a rolling N*86400-ms window" (which would span N+1
  distinct UTC dates and produce off-by-one buckets at non-midnight
  call times). Computed via:
    for (let i = days-1; i >= 0; i--)
      dates.push(_utcDateFromMs(now - i*86400*1000));

cacheHitRateWindow denominator: hit_rate = hit / (hit + miss).
Bypass is intentional non-cacheable (Anthropic cache_control marker),
NOT a cache miss; excluding it from the denominator gives a clean
cache-effectiveness signal.

TESTS — Suite 23, +27 (544 → 571):

  23a-1..4: discoverAuditFiles (empty dir / live only / live+rotated /
    non-audit files ignored)
  23b-1..6: readAuditWindow (all-coverage / single-day / half-open
    exclusivity / empty window / missing files / malformed-skip with
    warn)
  23c-1..4: aggregateRequests (counts + status buckets + by_provider;
    by_owner_tier; median+p95 latency over realistic distribution;
    invalid windowMs rejection)
  23d-1..4: topFallbackChains (sort desc by count; limit truncation;
    fallback_hops=0 excluded; first_seen/last_seen carried)
  23e-1..3: spendTrendDaily (N-day range correctness — caught off-by-
    one during local run; populated day breakdown; empty day sparse-
    fill)
  23f-1..3: cacheHitRateWindow (overall + per-provider hit_rate;
    bypass not in denominator; cache_status=null events excluded)
  23g-1..3: PII guard for aggregateRequests / spendTrendDaily /
    topFallbackChains + cacheHitRateWindow — every output JSON-
    stringified + scanned for forbidden PII keys

DOCUMENTATION:

  - AGENTS.md: lib/audit-query.mjs new entry; lib/audit.mjs note added
    that D52 extends with daily rotation.

NOT IN D49 scope:

  - server.mjs endpoints consuming these queries (D50)
  - dashboard.html (D51)
  - lib/audit.mjs rotation extension + bin/olp-audit-rotate.mjs (D52)
  - tried_providers schema fix (D53; D45 P2 deferral)
  - Phase 3 close → v0.3.0 (D55; maintainer-triggered)

Test count: 544 → 571 (+27). Verified locally via npm test.

AUTHORITY:

  - ADR 0008 § 4 (query API surface) + § 5 (rotation file naming
    pattern) + § 3 (storage layout).
  - ADR 0007 § 8 (audit ndjson event schema — input data).
  - CLAUDE.md release_kit overlay phase_rolling_mode — under
    Unreleased.
  - Standing autopilot grant.

ALIGNMENT.md scope check: this PR adds a new lib/ module. No provider
plugin / entry surface / IR change. Rule 5 commit-citation requirements
for those scopes do not apply.

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

AGENTS.md

@@ -39,7 +39,8 @@ Runtime: Node.js (ESM, `.mjs` throughout). No build step. No bundler. `server.mj
 - `lib/fallback/` — fallback engine (trigger detection, chain advancement, idempotent-failure safety, header annotation). Governed by ADR 0004.
 - `lib/keys.mjs` — multi-key auth, per-key namespacing, identity layer. Carries OCP's per-key isolation model into OLP. **✅ Phase 2 — D44 core + D45 server integration + D46 owner gating shipped (validateKey on every /v1/* + /health; chain filtered by providers_enabled; touchLastUsed fires post-response; /health payload trimmed for non-owner; X-OLP-Fallback-Detail gated by fallback_detail_header_policy).**
 - `bin/olp-keys.mjs` — keygen CLI bootstrap surface per ADR 0007 § 9.1. **✅ Shipped at D47.** Subcommands: `keygen [--owner|--name=X|--providers=csv|--force]`, `list [--owner-only|--include-revoked]`, `revoke --id=X`. Plaintext token printed once on keygen. Installed via `package.json bin` so `npx olp-keys ...` works (also `npm run olp-keys ...`).
-- `lib/audit.mjs` — append-only ndjson audit per ADR 0007 § 6.2 + § 8. **🟡 D45 — appendAuditEvent + getAuditDropCount shipped. Fires per /v1/chat/completions + /v1/models request including 401/403/5xx paths. Warn+1-retry on append failure; no memory buffer at Phase 2 (forward path).**
+- `lib/audit.mjs` — append-only ndjson audit per ADR 0007 § 6.2 + § 8. **🟡 D45 — appendAuditEvent + getAuditDropCount shipped. Fires per /v1/chat/completions + /v1/models request including 401/403/5xx paths. Warn+1-retry on append failure; no memory buffer at Phase 2 (forward path).** **D52 will extend with daily rotation per ADR 0008 § 5.**
+- `lib/audit-query.mjs` — audit ndjson aggregate query layer per ADR 0008 § 4. **🟡 D49 — discoverAuditFiles + readAuditWindow + aggregateRequests + topFallbackChains + spendTrendDaily + cacheHitRateWindow shipped. Cross-file walk over `audit.ndjson` (live) + `audit-YYYY-MM-DD.ndjson` (rotated). PII guard: aggregate shapes never include message content. In-memory scan per request (ADR 0008 Lane 2 = A; SQLite hybrid deferred to ADR 0007 § 13 trigger).**
 - `dashboard.html` — owner-only multi-provider dashboard (quota panels, fallback rate, cache hit rate). **📋 Planned (Phase 6) — not yet authored.**
 - `models-registry.json` — single source of truth for `(provider, model) → metadata`. SPOT.
 - `ALIGNMENT.md` — the constitution. Binding for any plugin / entry-surface / IR change.