fix(daemon): keep question-form close-tag scan Unicode-safe in the daemon mirror

The mirrored renderable-form check lowercased the whole buffer before
indexing the close tag. Some code points expand under toLowerCase ('İ' ->
'i̇'), shifting every offset after them, so closeIdx desynced from openEnd
(original-string coordinate) and the JSON body slice was corrupted —
failing a valid form when a casing-expanding char preceded it.

Mirror the web parser's findCloseTag: scan char-by-char and lowercase each
fixed-length candidate slice, returning an index in the original-string
space. Added a daemon regression with an 'İ' preamble before a valid form.

Addresses Looper review feedback on #3640.

apps/daemon/src/server.ts

@@ -2573,6 +2573,23 @@ function questionFormBodyIsRenderable(body) {
   return Array.isArray(questions) && questions.some((q) => q && typeof q === 'object');
 }
 
+// Locate `closeTag` (case-insensitively) at or after `from`, returning an
+// index in the ORIGINAL `text` coordinate space. Mirrors the web parser's
+// `findCloseTag`: scanning char-by-char and lowercasing each fixed-length
+// candidate slice keeps the result aligned with `openEnd`. Lowercasing the
+// whole string up front instead would desync the index, because some code
+// points expand under `toLowerCase()` (e.g. `"İ" -> "i̇"`) and shift every
+// offset after them — corrupting the body slice and failing a valid form.
+function findQuestionFormCloseTag(text, from, closeTag) {
+  const closeLower = closeTag.toLowerCase();
+  const tagLen = closeTag.length;
+  const maxStart = text.length - tagLen;
+  for (let i = from; i <= maxStart; i++) {
+    if (text.slice(i, i + tagLen).toLowerCase() === closeLower) return i;
+  }
+  return -1;
+}
+
 // Whether the agent's visible text contains a *renderable* clarifying form —
 // a closed `<question-form>`/`<ask-question>` block whose body satisfies the
 // parser contract above. The plugin-authoring missing-artifacts guard treats
@@ -2586,7 +2603,6 @@ function questionFormBodyIsRenderable(body) {
 // `packages/contracts` if the two drift.
 function emittedRenderableQuestionForm(text) {
   if (typeof text !== 'string' || !text) return false;
-  const lower = text.toLowerCase();
   let cursor = 0;
   while (cursor < text.length) {
     const m = QUESTION_FORM_OPEN_RE.exec(text.slice(cursor));
@@ -2594,7 +2610,7 @@ function emittedRenderableQuestionForm(text) {
     const tagName = (m[1] ?? 'question-form').toLowerCase();
     const closeTag = `</${tagName}>`;
     const openEnd = cursor + m.index + m[0].length;
-    const closeIdx = lower.indexOf(closeTag, openEnd);
+    const closeIdx = findQuestionFormCloseTag(text, openEnd, closeTag);
     if (closeIdx === -1) return false;
     if (questionFormBodyIsRenderable(text.slice(openEnd, closeIdx))) return true;
     cursor = closeIdx + closeTag.length;

apps/daemon/tests/chat-route.test.ts

@@ -727,6 +727,68 @@ process.stdin.on('end', () => {
       },
     );
   });
+  it('does not fail plugin authoring when a valid form follows a Unicode preamble that expands under toLowerCase', async () => {
+    // The mirrored close-tag scan must stay in the original-string coordinate
+    // space. Some code points expand under toLowerCase ("İ" -> "i̇"), so
+    // lowercasing the whole buffer before indexing would desync the close-tag
+    // offset and corrupt the JSON body slice, failing a valid form. The
+    // preamble here contains "İ" before a well-formed form block.
+    const projectId = `proj-plugin-authoring-unicode-${randomUUID()}`;
+
+    const createProjectResponse = await fetch(`${baseUrl}/api/projects`, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({
+        id: projectId,
+        name: 'Plugin authoring unicode-preamble fixture',
+        skillId: null,
+        designSystemId: null,
+      }),
+    });
+    expect(createProjectResponse.status).toBe(200);
+    const conversationsResponse = await fetch(`${baseUrl}/api/projects/${projectId}/conversations`);
+    expect(conversationsResponse.status).toBe(200);
+    const conversationsBody = await conversationsResponse.json() as {
+      conversations: Array<{ id: string }>;
+    };
+    const conversationId = conversationsBody.conversations[0]?.id;
+    expect(conversationId).toBeTruthy();
+
+    await withFakeAgent(
+      'opencode',
+      `
+process.stdin.resume();
+process.stdin.on('end', () => {
+  console.log(JSON.stringify({ type: 'step_start' }));
+  console.log(JSON.stringify({ type: 'text', part: { text: 'İstanbul brief — 先确认几个问题。\\n<ask-question id="discovery" title="Plugin brief">\\n{"questions":[{"id":"purpose","label":"What should it do?","type":"text"}]}\\n</ask-question>' } }));
+  console.log(JSON.stringify({ type: 'step_finish', part: { tokens: { input: 1, output: 1 } } }));
+  process.exit(0);
+});
+`,
+      async () => {
+        const createResponse = await fetch(`${baseUrl}/api/runs`, {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({
+            agentId: 'opencode',
+            projectId,
+            conversationId,
+            pluginId: 'od-plugin-authoring',
+            message: '帮我做个插件。',
+          }),
+        });
+        expect(createResponse.status).toBe(202);
+        const { runId } = await createResponse.json() as { runId: string };
+
+        const eventsResponse = await fetch(`${baseUrl}/api/runs/${runId}/events`);
+        const eventsBody = await readSseUntil(eventsResponse, 'event: final');
+        const statusBody = await waitForRunStatus(baseUrl, runId);
+
+        expect(eventsBody).not.toContain('ended before generating the required generated-plugin artifacts');
+        expect(statusBody.status).toBe('succeeded');
+      },
+    );
+  });
   it('closes the # Instructions block with an explicit "do not echo" guard so models do not parrot the prompt back', async () => {
     // claude-opus-4-7 (and a few other instruction-tuned models) start
     // their reply by echoing the # Instructions block verbatim, which