chore: D19 — cleanup batch (Findings 8 + 14 + 15 + D17 dead import)

cold-audit catch from 2026-05-23

Batched 4 small P3 mechanical cleanups per Iron Rule 11 IDR cleanup-batch
convention (all P3, all small, no semantic feature changes beyond defensive
validation).

Changes (7 files):

1. lib/ir/ir-to-openai.mjs (+30 / -3) — Finding 8 defensive validator:
   - Added OPENAI_FINISH_REASON_ENUM Set with the 6 spec-allowed values
     (stop / length / tool_calls / content_filter / function_call / null)
   - Added normalizeFinishReason(value) helper that returns value unchanged
     if in enum, else 'stop'
   - Routed both irChunkToOpenAISSE (streaming path) and
     irResponseToOpenAINonStream (non-stream path) through the helper
   - Bonus tightening (in-scope, same finish_reason concept):
     irResponseToOpenAINonStream's gate changed from `if (chunk.finish_reason)`
     (truthy check) to `if (chunk.finish_reason !== undefined)` so an
     explicit null (valid spec value meaning "still in progress") is no
     longer silently dropped by the truthy guard
   - Note: undefined → null collapse via `?? null` is unreachable in the
     current codebase (all provider plugins explicitly set finish_reason
     on stop chunks); defensive only against a future plugin that omits
     the field — documented inline

2. .github/workflows/alignment.yml (-16) — Finding 14 dead CI cleanup:
   - Removed `setup.mjs` from path triggers (push + pull_request) — the
     file does not exist in the repo
   - Removed the dead `KNOWN_PROVIDERS=(...)` bash array from job 1 and
     its comment block — no later step iterated over it, so the array
     was abandoned
   - LEFT untouched: the Node.js inline KNOWN_PROVIDERS array in the
     models-registry validation job — that one is actively consumed by
     the schema validation script

3. lib/providers/anthropic.mjs / codex.mjs / mistral.mjs (3 × 1 line) —
   Finding 15: removed unused `PROVIDER_ERROR_CODES` from import lines.
   Each line went from `import { ProviderError, PROVIDER_ERROR_CODES } from
   './base.mjs';` to `import { ProviderError } from './base.mjs';`. The
   constant remains exported from base.mjs (its declaration site, where
   it IS used for validation).

4. server.mjs (1 line) — D17 reviewer's observation: removed unused
   `getProviderForModel` from the import line. The function is only
   called by lib/fallback/engine.mjs which imports it directly from
   lib/providers/index.mjs. server.mjs's import was dead (the routing
   SPOT lives in engine.mjs after D17 — server.mjs uses buildDefaultChain
   exclusively).

5. test-features.mjs (+44) — Suite 3 (irChunkToOpenAISSE format) extended
   with 4 new finish_reason normalization tests:
   - Test 1: non-spec streaming finish_reason ('timeout', 'overloaded',
     'cancelled') → mapped to 'stop'
   - Test 2: spec-enum streaming finish_reason (all 6 incl. null) preserved
   - Test 3: non-spec non-stream finish_reason → mapped to 'stop'
   - Test 4: spec-enum non-stream finish_reason preserved (null
     intentionally omitted — documented inline)

Tests: 324 → 328 (+4). All pass on Node 20.

Pre-commit fold-ins (per evidence-first checkpoint #4):

- **D19 reviewer suggestion #1**: added inline comment to
  normalizeFinishReason explaining the unreachable `undefined → null`
  branch (defensive only, no current plugin omits the field). Cheap
  future-reader clarity.
- **D19 reviewer suggestion #2**: added inline comment to Test 4
  explaining why null is intentionally omitted from the spec-enum list
  (non-stream `!== undefined` gate enters with null and overwrites
  default 'stop' to null — semantically odd but spec-valid).

Reviewer suggestion #3 (consider stricter `undefined → 'stop'` on
streaming-stop path vs `null → null` on delta path) explicitly marked
out of scope by reviewer — would require call-site context awareness;
filed mentally as potential future work, not tracked as an issue
since no current path triggers it.

Authority:
- ALIGNMENT.md Rule 2(b) — only spec-defined fields in OpenAI responses
- OpenAI Chat Completions spec finish_reason enum
  https://platform.openai.com/docs/api-reference/chat/object#finish_reason
- CC 开发铁律 v1.6 § 10.x — Cold Audit Findings 8 / 14 / 15

Reviewer (Iron Rule v1.6 § 10.x Mode A, fresh-context opus, independent
of drafter): APPROVE. Verified the unreachable `undefined → null` branch
claim by grep-checking all 3 provider plugins (none emit undefined);
verified the two KNOWN_PROVIDERS arrays were correctly distinguished
(only the dead bash one removed); ran npm test independently to confirm
328/328.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

test-features.mjs

@@ -391,6 +391,57 @@ describe('irChunkToOpenAISSE format', () => {
     assert.equal(resp.choices[0].finish_reason, 'stop');
     assert.equal(resp.usage.total_tokens, 7);
   });
+
+  it('normalizeFinishReason: non-spec streaming finish_reason is mapped to stop', () => {
+    for (const bad of ['timeout', 'overloaded', 'cancelled']) {
+      const sse = irChunkToOpenAISSE({ type: 'stop', finish_reason: bad }, ID, MODEL);
+      const payload = JSON.parse(sse.slice(6).trim());
+      assert.equal(payload.choices[0].finish_reason, 'stop',
+        `non-spec value '${bad}' must be normalized to 'stop'`);
+    }
+  });
+
+  it('normalizeFinishReason: spec-enum streaming finish_reason values are preserved', () => {
+    const specValues = ['stop', 'length', 'tool_calls', 'content_filter', 'function_call', null];
+    for (const v of specValues) {
+      const sse = irChunkToOpenAISSE({ type: 'stop', finish_reason: v }, ID, MODEL);
+      const payload = JSON.parse(sse.slice(6).trim());
+      assert.equal(payload.choices[0].finish_reason, v,
+        `spec-enum value ${JSON.stringify(v)} must be preserved`);
+    }
+  });
+
+  it('normalizeFinishReason: non-spec non-stream finish_reason is mapped to stop', () => {
+    for (const bad of ['timeout', 'overloaded', 'cancelled']) {
+      const chunks = [
+        { type: 'delta', content: 'hi' },
+        { type: 'stop', finish_reason: bad },
+      ];
+      const resp = irResponseToOpenAINonStream(chunks, ID, MODEL);
+      assert.equal(resp.choices[0].finish_reason, 'stop',
+        `non-spec value '${bad}' must be normalized to 'stop' in non-stream path`);
+    }
+  });
+
+  it('normalizeFinishReason: spec-enum non-stream finish_reason values are preserved', () => {
+    // Note: null is intentionally omitted from this list. In the non-stream path,
+    // the condition `if (chunk.finish_reason !== undefined)` enters with null,
+    // overwrites the default 'stop' to null, and the response then carries
+    // finish_reason: null — meaning "still in progress" on a finalized completion,
+    // which is semantically odd but spec-valid. The non-stream path's behavior is
+    // documented by this omission rather than enforced (no plugin currently emits
+    // null on a non-stream stop chunk).
+    const specValues = ['stop', 'length', 'tool_calls', 'content_filter', 'function_call'];
+    for (const v of specValues) {
+      const chunks = [
+        { type: 'delta', content: 'hi' },
+        { type: 'stop', finish_reason: v },
+      ];
+      const resp = irResponseToOpenAINonStream(chunks, ID, MODEL);
+      assert.equal(resp.choices[0].finish_reason, v,
+        `spec-enum value '${v}' must be preserved in non-stream path`);
+    }
+  });
 });
 
 // ── Suite 4: Provider contract validation ─────────────────────────────────