test(coverage): add regression tests for issues #192, #206, #204

Additive test coverage across server, editor-ext, client and mcp.

#192 — AiChatService.stream integration (Section 3, against real Postgres):
- new apps/server/test/integration/ai-chat-stream.int-spec.ts drives the real
  streamText through a seeded ai/test MockLanguageModelV3 and a real Node
  ServerResponse, covering: onError persists an assistant error record
  (status 'error' + partial answer + provider cause in metadata); external MCP
  client closed exactly once on BOTH onFinish and onError; anti-tamper —
  history is rebuilt from the DB transcript, not from body.messages.

#206 — red-team findings (most already fixed+tested in #212):
- mdrt-2 (UNFIXED, data loss): turndown.dataloss.test.ts documents that
  pageBreak / transclusionReference / mention are silently dropped on Markdown
  export (characterization + it.fails for the desired survive-export contract).
- persist-6 (UNFIXED, data loss): persistence-store.spec.ts adds an it.failing
  documenting that a momentarily-empty live doc overwrites non-empty content
  (left unfixed — a store-side empty-guard is a behaviour change).

#204 — test-strategy plan, highest-priority subset:
- Phase 1: mcp-clients.lease.spec.ts covers the external MCP client
  lease/refcount/eviction lifecycle (leak / premature-close / double-close).
- Phase 2 data-integrity pure functions: editor-ext table-utils
  (transpose/moveRow/convert round-trip) and math tokenizer false-positive
  guard; client emoji-menu (+ it.fails for the unguarded localStorage
  JSON.parse bug), sort-cells, normalizeTableColumnWidths; mcp htmlEmbed/
  pageBreak markdown data-loss + footnote-diff; server export
  getInternalLinkPageName extensionless-path bug — FIXED (small/clear) + tested.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/integrations/export/utils.spec.ts

@@ -146,6 +146,19 @@ describe('getInternalLinkPageName', () => {
     expect(getInternalLinkPageName('Parent/My%20Page.md')).toBe('My Page');
   });
 
+  it('keeps the full basename when the path has no extension (#204)', () => {
+    // An extensionless link target must NOT be stripped to an empty string —
+    // there is no extension to drop. Previously `.split('.').slice(0,-1)`
+    // collapsed "My Page" to "" and the internal link rendered with no text.
+    expect(getInternalLinkPageName('Parent/My%20Page')).toBe('My Page');
+    expect(getInternalLinkPageName('Just A Name')).toBe('Just A Name');
+  });
+
+  it('preserves dots in a dotted name that has a real extension (#204)', () => {
+    // "v1.2.md" -> "v1.2": only the final ".md" segment is the extension.
+    expect(getInternalLinkPageName('docs/v1.2.md')).toBe('v1.2');
+  });
+
   it('falls back to the raw name without throwing on malformed encoding', () => {
     // "%E0%A4" is an incomplete escape; decodeURIComponent throws and the
     // helper returns the raw (still-encoded) name.