fix+test+docs: D53 — tried_providers schema semantic fix (D45 P2 deferral closed) (#30)

Sixth Phase 3 D-day. Small focused fix for the D45 fresh-context opus
reviewer P2 finding that was deferred: auditCtx.tried_providers on the
key_no_provider_access 403 path was being stamped with the ORIGINAL
chain (which was filtered out, never dispatched), distorting downstream
audit queries like "which providers did key X actually call".

CHANGES:

  - server.mjs handleChatCompletions ~L815: on key_no_provider_access
    403, auditCtx.tried_providers = [] (was _originalChainProviders).
    The configured-but-blocked chain still appears in the human-
    readable error message body — the audit just doesn't claim those
    providers were "tried" when the server's filter dispatched zero.

  - docs/adr/0007-multi-key-auth.md § 8 amendment: new paragraph
    spelling out the tried_providers semantic. "The list of providers
    the server actually dispatched a spawn against. A provider that
    was configured in the chain but filtered out by providers_enabled
    gating is NOT included — the key didn't try the provider, the
    gate did. On the 403 path tried_providers is the empty array."
    Plus a forward note that audit log rotation moved to Phase 3 /
    ADR 0008 § 5.

  - test-features.mjs Suite 20h-extra-audit (+1 test — 600 → 601):
    creates guest key with providers_enabled: ['mistral']; fires
    request for Anthropic-routed model; asserts 403
    key_no_provider_access; reads audit row from audit.ndjson;
    asserts tried_providers === []. Pins the D53 semantic against
    regression.

  - CHANGELOG.md: D53 entry under Unreleased.

NOT IN D53:

  - E2E + docs polish (D54)
  - Phase 3 close → v0.3.0 (D55; maintainer-triggered)

Test count: 600 → 601 (+1). Verified locally via npm test.

AUTHORITY:

  - ADR 0007 § 8 amendment (D53, 2026-05-25).
  - D45 fresh-context opus reviewer P2 deferral note.
  - CLAUDE.md release_kit overlay phase_rolling_mode — under Unreleased.
  - Standing autopilot grant.

ALIGNMENT.md scope check: small entry-surface change (audit context
field assignment on one error path) + ADR amendment + new test. Per
ALIGNMENT.md Rule 1 the ADR amendment is the authority citation for
the server change. No provider plugin / IR / models-registry change.

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

docs/adr/0007-multi-key-auth.md

@@ -263,7 +263,9 @@ Field origin:
 
 **No PII.** Audit deliberately captures NO request body, NO response body, NO IR-message content. Hash + shape only. This is a personal/family deployment property; do not relax without a separate ADR amendment.
 
-**Rotation.** Phase 2 does NOT rotate `audit.ndjson`. Rotation policy lands in Phase 3 alongside Dashboard / audit query work (§ 12).
+**`tried_providers` semantics (clarification, D53 / 2026-05-25).** The field captures the list of providers the server **actually dispatched a spawn against** for this request. A provider that was configured in the chain but filtered out by `providers_enabled` gating (resulting in 403 `key_no_provider_access`) is NOT included — the key didn't try the provider, the gate did. On the 403 path `tried_providers` is the empty array. The configured-but-blocked chain providers appear in the human-readable error message returned to the client but are intentionally NOT surfaced in the audit event, so downstream queries like "which providers did key X actually call" stay accurate. This semantic was implicit in the D45 implementation (where the field was set to the original chain on 403, misrepresenting "tried"); D53 corrects the implementation + amends this section to spell out the intent.
+
+**Rotation.** Phase 2 does NOT rotate `audit.ndjson`. Rotation policy ships in Phase 3 — daily rotation via `lib/audit.mjs` `_maybeRotateAudit` synchronous trigger on first append after UTC date change + optional `bin/olp-audit-rotate.mjs` external cron. See ADR 0008 § 5.
 
 ---