Keep repository language stats aligned with authored TypeScript

The runtime wrappers and maintenance scripts stay in JavaScript, but GitHub's
repository language bar should reflect the authored product source instead of
auxiliary script formats. This adds Linguist detectability overrides in
`.gitattributes` and locks them in the documentation governance suite.

Constraint: Wrapper and maintenance scripts must remain directly executable without build pipeline changes
Rejected: Convert scripts and wrappers to TypeScript | would widen runtime and packaging scope beyond a metadata-only change
Confidence: high
Scope-risk: narrow
Directive: If a non-TypeScript repo artifact should count toward the language bar later, update `.gitattributes` and `test/documentation.test.ts` together
Tested: `git check-attr linguist-detectable -- index.ts scripts/codex.js scripts/check-pack-budget.mjs scripts/test-all-models.sh lib/oauth-success.html`; `npm test -- test/documentation.test.ts`; `npm run lint`; `npm run typecheck`; `npm run build`
Not-tested: Full `npm test` remains red on inherited `test/proactive-refresh.test.ts` timeouts reproduced on clean `origin/main`

Author: ndycode

.gitattributes

@@ -0,0 +1,6 @@
+# Keep repository language stats focused on authored TypeScript sources.
+*.ts linguist-detectable
+*.js -linguist-detectable
+*.mjs -linguist-detectable
+*.sh -linguist-detectable
+*.html -linguist-detectable

test/documentation.test.ts

@@ -609,6 +609,21 @@ function compareSemverDescending(left: string, right: string): number {
 		expect(conduct).toContain("security.md");
 	});
 
+	it("locks linguist overrides for a TypeScript-only repository language bar", () => {
+		const gitattributes = ".gitattributes";
+		expect(
+			existsSync(join(projectRoot, gitattributes)),
+			`${gitattributes} should exist`,
+		).toBe(true);
+
+		const content = read(gitattributes);
+		expect(content).toContain("*.ts linguist-detectable");
+		expect(content).toContain("*.js -linguist-detectable");
+		expect(content).toContain("*.mjs -linguist-detectable");
+		expect(content).toContain("*.sh -linguist-detectable");
+		expect(content).toContain("*.html -linguist-detectable");
+	});
+
 	it("publishes maintainer runbooks for refactor-era changes", () => {
 		const docsPortal = read("docs/README.md");
 		const testingGuide = read("docs/development/TESTING.md");