feat(page-data): add validation suggestions, repair path, and thinking fixes

Map Page Data failure codes to Chinese remediation hints, trigger one-shot
goosed repair for remediable cases, and recover poisoned thinking sessions.
Route local DeepSeek through the no-think proxy via host.docker.internal so
tool rounds no longer hit reasoning_content 400; document gate and case-study
scenarios for event registration repair.

Co-authored-by: Cursor <cursoragent@cursor.com>

llm-providers.test.mjs

@@ -212,6 +212,52 @@ test('create custom relay profile registers goosed custom provider', async () =>
   assert.equal(rows[0].provider_kind, 'custom');
 });
 
+test('deleteKey treats a missing TKMind custom provider as already deleted', async () => {
+  const row = {
+    id: 'key-relay',
+    provider_id: CUSTOM_PROVIDER_ID,
+    provider_kind: 'custom',
+    goosed_provider_id: 'custom_relay_buyer_ollama',
+    name: 'Relay Buyer Ollama',
+    status: 'active',
+    is_selected: 0,
+  };
+  let deleted = false;
+  const pool = {
+    async query(sql, params = []) {
+      if (sql.includes('SELECT * FROM h5_llm_provider_keys WHERE id = ?')) {
+        return [[params[0] === row.id ? row : null].filter(Boolean)];
+      }
+      if (sql.includes('DELETE FROM h5_llm_provider_keys WHERE id = ?')) {
+        deleted = params[0] === row.id;
+        return [[]];
+      }
+      throw new Error(`Unexpected SQL: ${sql}`);
+    },
+  };
+  const mockFetch = async (_url, init = {}) => {
+    assert.equal(init.method, 'DELETE');
+    return {
+      ok: false,
+      status: 500,
+      text: async () => JSON.stringify({
+        message: 'Provider not found: custom_relay_buyer_ollama',
+      }),
+    };
+  };
+  const service = createLlmProviderService(pool, {
+    apiTarget: 'https://127.0.0.1:18006',
+    apiSecret: 'secret',
+    encryptionKey: 'unit-test-secret',
+    apiFetchImpl: mockFetch,
+  });
+
+  const result = await service.deleteKey(row.id);
+
+  assert.equal(result.ok, true);
+  assert.equal(deleted, true);
+});
+
 test('selectKey rejects disabled profile', async () => {
   const row = {
     id: 'key-1',
@@ -774,7 +820,13 @@ test('syncProfileToGoosed routes local DeepSeek through the no-thinking proxy',
         init.method === 'PUT'
         && href.includes(`/config/custom-providers/${MEMIND_DEEPSEEK_NO_THINK_PROVIDER_ID}`)
       ) {
-        return { ok: false, status: 404, text: async () => '' };
+        return {
+          ok: false,
+          status: 500,
+          text: async () => JSON.stringify({
+            message: `Provider not found: ${MEMIND_DEEPSEEK_NO_THINK_PROVIDER_ID}`,
+          }),
+        };
       }
       if (init.method === 'POST' && href.endsWith('/config/custom-providers')) {
         return {