feat: D80 — anthropic plan-usage probe port (Phase 5) (#52)

Port OCP server.mjs:842-1109 plan-usage probe to lib/providers/anthropic.mjs:quotaStatus().

## Authority citations (CLAUDE.md hard requirement #1)

1. Schema pin: ~/.cc-rules/memory/learnings/anthropic_plan_usage_probe_schema_2026_05_26.md
   — 13-field canonical schema verified live 2026-05-26; 3 fields new vs OCP
   2026-04 capture (5h-status, 7d-status, overage-reset).

2. OCP port source: OCP server.mjs:842-1109 — usageCache, oauthRefreshBackoff,
   getOAuthCredentials, refreshOAuthToken, fetchUsageFromApi, parseRateLimitHeaders.
   Claude Code CLI uses this same POST /v1/messages internally (verified 2026-05-26
   by `strings` on @anthropic-ai/claude-code v2.1.142 / v2.1.150 Mach-O binary — see
   audit memory). This is observed CLI behaviour, not invention.

3. ADR 0002 Amendment 8 — READ-ONLY exemption for quotaStatus() direct-API access.
   Three constraints satisfied: READ-ONLY (max_tokens:1, body discarded),
   subscription-scope (same readAuthArtifact() creds as spawn path),
   idempotent-failure (returns null / stale on any error, never throws).

4. ADR 0013 — OAuth READ-ONLY consumption rules. All 7 rules satisfied:
   Rule 1: credential reuse via readAuthArtifact() (env → .credentials.json → keychain).
   Rule 2: only POST /v1/messages (no other endpoints). Body discarded; headers-only.
   Rule 3: 5min TTL cache; 60s–3600s exponential backoff; stale-on-failure.
   Rule 4: opt-in via ~/.olp/config.json providers.anthropic.quota_probe_enabled (default false).
   Rule 5: schema pin committed to memory file; drift detection protocol in place.
   Rule 6: doctor check anthropic.quota_probe_reachable surfaces probe status.
   Rule 7: does not govern spawn-path refresh (separate concern).

5. ADR 0012 D80 — Phase 5 charter: this commit is the D80 deliverable.

## Live probe transcript (2026-05-26 from MacBook keychain OAuth credentials)

Path B verification per ADR 0013 Rule 5:
  curl -s -i -m 20 -X POST https://api.anthropic.com/v1/messages \
    -H "Authorization: Bearer <token>" \
    -H "anthropic-beta: oauth-2025-04-20" \
    -H "anthropic-version: 2023-06-01" \
    -H "Content-Type: application/json" \
    -d '{"model":"claude-haiku-4-5-20251001","max_tokens":1,"messages":[{"role":"user","content":"."}]}'

Response (header lines only):
  HTTP/2 200
  anthropic-ratelimit-unified-status: allowed
  anthropic-ratelimit-unified-5h-status: allowed
  anthropic-ratelimit-unified-5h-reset: 1779794400
  anthropic-ratelimit-unified-5h-utilization: 0.09
  anthropic-ratelimit-unified-7d-status: allowed
  anthropic-ratelimit-unified-7d-reset: 1780225200
  anthropic-ratelimit-unified-7d-utilization: 0.32
  anthropic-ratelimit-unified-representative-claim: five_hour
  anthropic-ratelimit-unified-fallback-percentage: 0.5
  anthropic-ratelimit-unified-reset: 1779794400
  anthropic-ratelimit-unified-overage-disabled-reason: org_level_disabled_until
  anthropic-ratelimit-unified-overage-status: rejected
  (no anthropic-ratelimit-unified-overage-reset — expected: only present on active overage)

12/13 fields present. overage-reset absent = no active overage (expected per audit memory).
All fields parsed correctly by _parseRateLimitHeaders(). Confirmed via D80 smoke test.

## Implementation

A. quotaStatus() — full probe implementation replacing D4 null stub:
   - _readProviderConfig('anthropic') gate (Rule 4 opt-in)
   - 5min module-level cache check (quotaProbeState.cache)
   - 60s–3600s exponential backoff check (quotaProbeState.backoffUntil / backoffMs)
   - readAuthArtifact() credential read (env → .credentials.json → macOS keychain)
   - _probeOnce() → POST /v1/messages with 4 required headers; body discarded
   - 401/403 → single refresh-and-retry via _refreshAccessToken()
   - On success: cache { fetchedAt, data } + reset backoff to MIN
   - On failure: _scheduleBackoff() (doubles backoffMs, caps at MAX) + return stale or null
   - Return shape: { probedAt, source, schemaVersion, stale, fields:{...13}, raw:{...} }

B. _parseRateLimitHeaders() — all 13 fields (3 new vs OCP):
   - status, representative_claim, reset, fallback_percentage (aggregate)
   - status_5h, utilization_5h, reset_5h (5h window)
   - status_7d, utilization_7d, reset_7d (7d window)
   - overage_status, overage_disabled_reason, overage_reset (overage)
   - Numeric strings → numbers; missing fields → null (not 0 or "unknown")

C. _refreshAccessToken() — uses Node.js built-in https (no fetch/3rd-party deps).
   Shared backoff state via quotaProbeState. Max one refresh per backoff window.

D. _probeOnce() — uses Node.js built-in https. 15s timeout. Drains + discards body.

E. _readProviderConfig() — reads ~/.olp/config.json providers.<name> block.
   OLP_HOME respected (same as lib/keys.mjs). Never throws; returns {} on error.

F. doctorChecks() — new anthropic.quota_probe_reachable check (ADR 0013 Rule 6):
   - status: ok when probe disabled (returns advisory message)
   - status: ok when probe succeeds (shows utilization %)
   - status: warn when stale cache exists (probe failed but cache present)
   - status: fail when no cache + probe failed (fix_commands + human_steps recipe)

G. docs/v1x-roadmap.md — #8 Dashboard enrichment entry (D79 follow-up) added.

## Tests

- All 720 existing tests pass (npm test).
- Suite 33j updated to include anthropic.quota_probe_reachable in the expected
  probe set (3 probes total, previously 2).
- D83 (Suite 38) will add quota-probe unit tests with mock HTTP server.

## What NOT changed

- dashboard.html — untouched (D82)
- lib/audit-query.mjs — untouched (D81)
- lib/providers/codex.mjs, mistral.mjs — untouched (D84 NO-GO per ADR 0012 Amendment 1)

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

test-features.mjs

@@ -14002,12 +14002,19 @@ describe('Suite 33 — D65 lib/doctor.mjs framework (ADR 0010 § Phase 4 D64-D67
   });
 
   it('33j — anthropic plugin doctorChecks() returns the documented probe set', () => {
-    // Plugin contract: ADR 0002 Amendment 7. anthropic.mjs ships
-    // anthropic.cli_available + anthropic.oauth_token_present.
+    // Plugin contract: ADR 0002 Amendment 7 (D67) + D80 (quota probe check).
+    // anthropic.mjs ships:
+    //   anthropic.cli_available (D67)
+    //   anthropic.oauth_token_present (D67)
+    //   anthropic.quota_probe_reachable (D80 — Phase 5, ADR 0013 Rule 6)
     const checks = anthropic.doctorChecks();
     assert.ok(Array.isArray(checks));
     const ids = checks.map(c => c.id).sort();
-    assert.deepEqual(ids, ['anthropic.cli_available', 'anthropic.oauth_token_present']);
+    assert.deepEqual(ids, [
+      'anthropic.cli_available',
+      'anthropic.oauth_token_present',
+      'anthropic.quota_probe_reachable',
+    ]);
     assert.ok(checks.every(c => c.category === 'provider'));
     assert.ok(checks.every(c => typeof c.run === 'function'));
   });