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/client/src/features/page/tree/model/tree-model.test.ts

@@ -196,6 +196,17 @@ describe('treeModel.insertByPosition', () => {
     const t = treeModel.insertByPosition(roots, null, node);
     expect(t.map((n) => n.id)).toEqual(['a', 'b', 'c', 'x']);
   });
+
+  it('tie-break: a node whose position EQUALS a sibling lands deterministically (strict >)', () => {
+    // The insertion index is the first sibling whose position sorts STRICTLY
+    // after the new node's. An equal sibling is not strictly after, so it is
+    // skipped — the new node lands immediately AFTER every equal-position
+    // sibling and before the first strictly-greater one. This is deterministic:
+    // a tie always resolves the same way on every client.
+    const node: P = { id: 'x', name: 'X', position: 'a2' }; // equals b's position
+    const t = treeModel.insertByPosition(roots, null, node);
+    expect(t.map((n) => n.id)).toEqual(['a', 'b', 'x', 'c']);
+  });
 });
 
 // addTreeNode idempotency: the receiver early-returns when the node id already
@@ -692,4 +703,45 @@ describe('treeModel.move', () => {
     });
     expect(out.tree).toBe(fixture);
   });
+
+  it('cross-parent move does NOT apply the same-parent adjust (no off-by-one)', () => {
+    // Source `x3` sits at index 2 in parent `x`; target `y1` sits at index 0 in
+    // parent `y`. sourceInfo.index (2) > info.index (0) AND the parents differ,
+    // so the `sameParent && source.index < info.index` adjust must be 0 — the
+    // node must land at index 0 in `y`, not at index -1 (which would silently
+    // drop it at a wrong slot / off-by-one).
+    const crossFixture: N[] = [
+      {
+        id: 'x',
+        name: 'X',
+        children: [
+          { id: 'x1', name: 'X1' },
+          { id: 'x2', name: 'X2' },
+          { id: 'x3', name: 'X3' },
+        ],
+      },
+      {
+        id: 'y',
+        name: 'Y',
+        children: [
+          { id: 'y1', name: 'Y1' },
+          { id: 'y2', name: 'Y2' },
+        ],
+      },
+    ];
+    const { tree: t, result } = treeModel.move(crossFixture, 'x3', {
+      kind: 'reorder-before',
+      targetId: 'y1',
+    });
+    expect(result).toEqual({ parentId: 'y', index: 0 });
+    expect(treeModel.find(t, 'y')?.children?.map((n) => n.id)).toEqual([
+      'x3',
+      'y1',
+      'y2',
+    ]);
+    expect(treeModel.find(t, 'x')?.children?.map((n) => n.id)).toEqual([
+      'x1',
+      'x2',
+    ]);
+  });
 });