test: cover features since 053a9c0d + repair test tooling

Add ~330 tests across server (Jest), client (Vitest), editor-ext (Vitest)
and packages/mcp (node:test) for the gitmost features added since
053a9c0d: AI chat, AI agent roles, public-share assistant, MCP per-user
auth, HTML embed, page templates/embed, realtime tree, tree
expand/collapse, and the AI-settings UI.

Test-tooling fixes (prerequisite, were silently hiding coverage):
- Repair 3 page-template specs broken by the 11-arg TransclusionService
  constructor; they never compiled, so template access-control / content
  -leak / unsync-strip coverage was fictitious.
- Build @docmost/editor-ext before server tests via a `pretest` hook;
  the stale dist omitted the new HtmlEmbed/PageEmbed exports (TS2305).
- Let jest resolve the .tsx email templates: add `tsx` to
  moduleFileExtensions and widen the ts-jest transform to (t|j)sx?.

Behaviour-preserving "extract pure core" refactors that the tests drive:
- server: resolveShareAssistantRequest + uiMessageTextLength
  (public-share controller), decideBasicGate + mapAuthResultToResponse
  (mcp), buildErrorAssistantRecord (ai-chat), jsonbObject export (roles).
- client: render-raw-html + shouldExecute/canEdit, decide-embed-state,
  page-embed picker utils, tree-socket reducers, open/close branch maps,
  isEndpointConfigured/resolveKeyField; buildTreeWithChildren now treats
  a permission-trimmed orphan as a root instead of crashing.

Deferred (need a test DB or HTTP harness, documented in the specs):
repo-level Postgres integration tests and the public-share XFF E2E.
Pre-existing DI/lib0-ESM suite failures are untouched and out of scope.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/src/core/ai-chat/ai-chat.service.ts

@@ -384,11 +384,7 @@ export class AiChatService {
         this.logger.error(`AI chat stream error: ${errorText}`, e?.stack);
         // Persist whatever text we have (likely empty) so the turn is recorded,
         // and record the error text in metadata so it is visible in history.
-        await persistAssistant({
-          text: '',
-          toolCalls: null,
-          metadata: { finishReason: 'error', parts: [], error: errorText },
-        });
+        await persistAssistant(buildErrorAssistantRecord(errorText));
         await closeExternalClients();
       },
       onAbort: async ({ steps }) => {
@@ -710,6 +706,26 @@ export function rowToUiMessage(row: AiChatMessage): Omit<UIMessage, 'id'> & {
   return { id: row.id, role, parts: parts as UIMessage['parts'] };
 }
 
+/**
+ * Build the assistant-message record persisted when a turn fails before any text
+ * is produced (the streamText onError path). Pure: it takes the formatted error
+ * text and returns the exact `{ text, toolCalls, metadata }` payload handed to
+ * persistAssistant, so the first-turn-failure recording shape is unit-testable
+ * without seaming streamText. The empty text + empty parts mean the failed turn
+ * is still recorded in history, with the provider cause visible in metadata.
+ */
+export function buildErrorAssistantRecord(errorText: string): {
+  text: string;
+  toolCalls: null;
+  metadata: { finishReason: 'error'; parts: []; error: string };
+} {
+  return {
+    text: '',
+    toolCalls: null,
+    metadata: { finishReason: 'error', parts: [], error: errorText },
+  };
+}
+
 /**
  * Reduce SDK step objects to a compact, JSON-serializable trace for the
  * `tool_calls` column. Stores only what the UI action-log and history need —