build: omit the standalone output target for contributor builds (#12204)

Completes the contributor profile: #12198 stopped OmniRoute from assembling the standalone bundle, but Next was still asked to emit one. Making output: "standalone" conditional on OMNIROUTE_BUILD_PROFILE=contributor removes the standalone tracing pass itself, which is where the remaining time went.

Default builds are unaffected — the flag is read from the env at config load and is false everywhere except the contributor profile, so tests/unit/next-config.test.ts still observes output === "standalone" (18/18 green across contributor-build-script, next-config and build-profile-stubs).

Reconciled on merge: CONTRIBUTING.md and scripts/build/backendOnlyPages.mjs already carried this stack's earlier steps on the tip, so both took the tip's side; only the next.config.mjs conditional and its test are this step's delta.

Thanks @rafacpti23 for splitting this into four reviewable steps — it made the whole stack easy to reason about.

next.config.mjs

@@ -109,6 +109,8 @@ function filterKnownInfrastructureWarnings(baseConsole) {
 // The resulting artifact is intended to be published as `omniroute-secure`
 // for security-sensitive environments. See docs/security/SOCKET_DEV_FINDINGS.md.
 const isMinimalBuild = process.env.OMNIROUTE_BUILD_PROFILE === "minimal";
+// Contributor builds validate compilation only and do not need a shippable standalone bundle.
+const isContributorBuild = process.env.OMNIROUTE_BUILD_PROFILE === "contributor";
 
 // #10273: `null` unless the operator opts in with DASHBOARD_ALLOW_EMBED=vscode. Read at build
 // time like every other knob in this file (OMNIROUTE_BASE_PATH, OMNIROUTE_BUILD_PROFILE, …),
@@ -218,7 +220,7 @@ const nextConfig = {
       },
     ],
   },
-  output: "standalone",
+  ...(isContributorBuild ? {} : { output: "standalone" }),
   compress: true,
   productionBrowserSourceMaps: false,
   // OmniRoute is a proxy for AI APIs — request bodies routinely include

tests/unit/build/contributor-build-script.test.mjs

@@ -7,6 +7,8 @@ import {
   stubContributorInstrumentation,
 } from "../../../scripts/build/backendOnlyPages.mjs";
 
+const nextConfigSource = fs.readFileSync(path.join(process.cwd(), "next.config.mjs"), "utf8");
+
 const packageJson = JSON.parse(fs.readFileSync(path.join(process.cwd(), "package.json"), "utf8"));
 
 test("contributor build profile selects the webpack fallback", () => {
@@ -48,3 +50,11 @@ test("contributor instrumentation stubs are reversible", async () => {
   for (const [target, source] of originals) assert.equal(await fs.readFile(target, "utf8"), source);
   await fs.rm(tempRoot, { recursive: true, force: true });
 });
+
+test("contributor profile disables standalone output while default keeps it", () => {
+  assert.match(nextConfigSource, /isContributorBuild/);
+  assert.match(
+    nextConfigSource,
+    /\.\.\.\(isContributorBuild \? \{\} : \{ output: "standalone" \}\)/
+  );
+});