test(coding-agent): fixed environment-sensitive and stale-trigger test failures

- Shimmed writable select.value in export-html harness; linkedom's getter-only HTMLSelectElement.value made template.js theme assignment throw under strict mode.
- Bound the oauth-flow port blocker to 127.0.0.1 explicitly; macOS lets a specific-address bind coexist with a wildcard one, so the flow bound the blocked port and never fell back.
- Re-anchored atomic-rewrite race tests on rewriteEntries() after the compaction-supersede rewrite trigger was removed in cb63ebd.

packages/coding-agent/test/export-html-markdown.test.ts

@@ -45,6 +45,19 @@ function renderSession(session: MinimalSession) {
 		value: () => ({ matches: false, addEventListener() {}, removeEventListener() {} }),
 		configurable: true,
 	});
+	// linkedom's HTMLSelectElement.value is getter-only; template.js assigns it
+	// under 'use strict', which would throw. Shim a writable value like a browser.
+	const themeSelect = document.getElementById("theme-select");
+	if (themeSelect) {
+		let themeValue = "auto";
+		Object.defineProperty(themeSelect, "value", {
+			get: () => themeValue,
+			set: next => {
+				themeValue = String(next);
+			},
+			configurable: true,
+		});
+	}
 
 	const context = vm.createContext({
 		window,

packages/coding-agent/test/oauth-flow.test.ts

@@ -540,7 +540,10 @@ describe("mcp oauth flow", () => {
 		// Here `clientId` is unset, so `MCPOAuthFlow.#tryRegisterClient` will
 		// register the actual fallback URI with the provider and the
 		// authorization request will use that fresh client_id.
-		const blocker = Bun.serve({ port: 0, fetch: () => new Response("blocker") });
+		// Occupy 127.0.0.1 explicitly — the interface callback flows bind for
+		// `localhost` — because macOS lets a specific-address bind coexist with a
+		// wildcard one, which would let the flow bind the "blocked" port.
+		const blocker = Bun.serve({ hostname: "127.0.0.1", port: 0, fetch: () => new Response("blocker") });
 		const blockerPort = blocker.port;
 		if (typeof blockerPort !== "number") {
 			blocker.stop(true);

packages/coding-agent/test/session-manager-atomic-rewrite-race.test.ts

@@ -177,6 +177,8 @@ describe("SessionManager atomic rewrite race", () => {
 		sessionManager.appendCompaction("older summary", "older", firstKeptEntryId, 100);
 		await sessionManager.flush();
 		sessionManager.appendCompaction("newer summary", "newer", firstKeptEntryId, 80);
+		// Kick off a full-file rewrite that parks inside the fake storage until released.
+		const rewritePublished = sessionManager.rewriteEntries();
 		await storage.rewriteStarted.promise;
 
 		sessionManager.appendMessage({ role: "user", content: "during rewrite prompt", timestamp: Date.now() });
@@ -185,6 +187,7 @@ describe("SessionManager atomic rewrite race", () => {
 		const titlePersisted = sessionManager.setSessionName("Post rewrite title", "user", "test");
 
 		storage.allowRewrite.resolve();
+		await rewritePublished;
 		await titlePersisted;
 		await sessionManager.flush();
 		sessionManager.appendMessage({
@@ -288,9 +291,10 @@ describe("SessionManager atomic rewrite race", () => {
 		if (!firstKeptEntryId) throw new Error("Expected seeded branch entry");
 		sessionManager.appendCompaction("older summary", "older", firstKeptEntryId, 100);
 		await sessionManager.flush();
-		// Second compaction elides the first, scheduling a full-file rewrite that
-		// parks inside the fake storage until we release it.
 		sessionManager.appendCompaction("newer summary", "newer", firstKeptEntryId, 80);
+		// Kick off a full-file rewrite that parks inside the fake storage until we
+		// release it.
+		const rewritePublished = sessionManager.rewriteEntries();
 		await storage.rewriteStarted.promise;
 
 		// Simulate a Ctrl+C teardown: append a session_exit custom entry (fenced
@@ -308,8 +312,7 @@ describe("SessionManager atomic rewrite race", () => {
 		// stale body serialized before flushSync bumped the disk epoch; otherwise
 		// the async publish would overwrite the durable exit record.
 		storage.allowRewrite.resolve();
-		await Promise.resolve();
-		await Promise.resolve();
+		await rewritePublished;
 
 		const afterRelease = await storage.readText(sessionFile);
 		expect(afterRelease).toContain('"customType":"session_exit"');