fix(tests): drain three base-reds left by the SSE-comment default and a locale gap (#10704)

* fix(tests): drain three base-reds left by the SSE-comment default and a locale gap

All three reproduce on a pristine tip; none is caused by the branch that found
them.

1. i18n vi — six keys landed in en.json without a Vietnamese counterpart
   (settings.reasoningTokenBuffer*, settings.zeroLatencyOptimizations*,
   settings.compressionOutputStyle.i-have-adhd.*). The vi locale is held to
   strict parity, so the whole i18n-vi suite went red. Translated; no existing
   key reordered.

2. chatcore-translation-paths — #10539 flipped OMNIROUTE_SSE_COMMENTS to
   off-by-default and updated three sibling tests, but not this one, which
   asserted the `: x-omniroute-*` trailer is emitted. The test now asserts the
   current contract (stream is comment-free, still ends with [DONE], metadata
   still travels in the X-OmniRoute-* headers). The opt-in half stays covered by
   sse-comments-optout-9305.test.ts, which drives the env var through all three
   states. Enabling the flag inside this file instead leaks process.env into its
   sibling call-log tests, which is how the first attempt turned one red into a
   different one.

3. chat-messages-validation-6402 — all nine Antigravity cases asserted
   `assert.match(body, /ok/)` against the mocked model output. That text never
   reached this layer: the match only ever succeeded on the "ok" inside
   `: x-omniroute-tokens-in=0`, an SSE comment trailer. When the trailers stopped
   being emitted the coincidence broke, not the behavior — bisected to
   6b823aa441, whose parent 6d99a46d4b passes. The test now asserts the guard it
   is named for (a cloudcode envelope must not be rejected by the #6402
   missing-messages validator). Real content-relay coverage for this provider
   lives in antigravity-streaming-passthrough.test.ts, which passes.

Verified: vi 5/5, chatcore-translation-paths 70/70, chat-messages-validation
14/14.

* chore(changelog): correct the fragment to the real PR number (#10704)

---------

Co-authored-by: Xiangzhe <bakryun0718@proton.me>

tests/unit/chat-messages-validation-6402.test.ts

@@ -171,8 +171,22 @@ for (const model of ANTIGRAVITY_GEMINI_MODELS) {
     assert.equal(upstreamCalled, true, "Antigravity request should reach the upstream executor");
     assert.equal(response.status, 200, "Antigravity cloudcode envelopes must not return 400");
 
+    // This assertion is the guard the test is named for: a cloudcode envelope has no
+    // `messages` key, so it must not be rejected by the #6402 validator.
+    //
+    // It used to read `assert.match(body, /ok/)`, aimed at the mocked upstream's
+    // "ok" text — but that text never reached this layer. The match only ever
+    // succeeded on the "ok" inside `: x-omniroute-tokens-in=0`, an SSE *comment*
+    // trailer. When #10539 flipped OMNIROUTE_SSE_COMMENTS to off-by-default the
+    // trailers stopped being emitted, the body went empty, and the coincidence —
+    // not the behavior — broke. Content relay for this provider is covered for
+    // real, at the executor level, by antigravity-streaming-passthrough.test.ts.
     const body = await response.text();
-    assert.match(body, /ok/);
+    assert.doesNotMatch(
+      body,
+      /messages.*Expected array/i,
+      "cloudcode envelope must not be caught by the missing-messages guard"
+    );
   });
 }
 

tests/unit/chatcore-translation-paths.test.ts

@@ -2597,7 +2597,7 @@ test("chatCore injects progress events into streaming responses when requested",
   assert.equal(result.response.headers.get("X-OmniRoute-Progress"), "enabled");
   assert.match(streamText, /event: progress/);
 });
-test("chatCore emits final SSE metadata comments before [DONE] on streaming responses", async () => {
+test("chatCore keeps the SSE stream comment-free by default and still ends with [DONE]", async () => {
   const { result } = await invokeChatCore({
     provider: "openai",
     model: "gpt-4o-mini",
@@ -2615,14 +2615,20 @@ test("chatCore emits final SSE metadata comments before [DONE] on streaming resp
   const streamText = await result.response.text();
 
   assert.equal(result.success, true);
+  // The per-request metadata reaches the client through these headers regardless
+  // of the comment setting — that is what makes the trailer optional.
   assert.equal(result.response.headers.get("X-OmniRoute-Provider"), "openai");
   assert.equal(result.response.headers.get("X-OmniRoute-Model"), "gpt-4o-mini");
-  assert.match(streamText, /: x-omniroute-response-cost=\d+\.\d{10}/);
-  assert.match(streamText, /: x-omniroute-tokens-in=\d+/);
-  assert.match(streamText, /: x-omniroute-tokens-out=\d+/);
-  assert.ok(
-    streamText.indexOf(": x-omniroute-response-cost=") < streamText.indexOf("data: [DONE]")
-  );
+
+  // #10524 flipped OMNIROUTE_SSE_COMMENTS to off-by-default: strict SSE clients
+  // JSON.parse every line and crash on `: x-omniroute-*` comments. This test used
+  // to assert the opposite and went red on the release branch when that default
+  // landed. The opt-in half — trailer present, after the finish chunk and before
+  // [DONE] — is owned by sse-comments-optout-9305.test.ts, which drives the env
+  // var through all three states; enabling it here instead leaks process.env into
+  // the sibling call-log tests in this file.
+  assert.doesNotMatch(streamText, /: x-omniroute-/);
+  assert.match(streamText, /data: \[DONE\]/);
 });
 test("buildStreamingResponseHeaders drops upstream compression and framing headers", () => {
   const headers = new Headers(