fix(test): remove jsdom pragma + add window stub DOM surface

A/B fix per WorkBuddy review:
- browser-globals.ts: add addEventListener/removeEventListener/dispatchEvent
  to window stub, add compatMode to document stub
- Remove // @vitest-environment jsdom from 5 specs that only use
  renderToString/createElement (SSR, no DOM needed)

Test Files 131 passed (131), Tests 1367 passed, EXIT=0

tests/browser-globals.ts

@@ -41,6 +41,9 @@ if (g.document === undefined) {
     querySelector: () => null,
     querySelectorAll: () => [],
     styleSheets: [],
+    // KaTeX probes compatMode at module load; without it it warns
+    // "doesn't work in quirks mode" and some layout paths no-op.
+    compatMode: 'CSS1Compat',
   }
 }
 
@@ -50,6 +53,9 @@ if (g.navigator === undefined) {
 
 if (g.window === undefined) {
   g.window = {
+    addEventListener: () => {},
+    removeEventListener: () => {},
+    dispatchEvent: () => true,
     clearTimeout: () => {},
     setTimeout: (_fn: () => void) => 0,
     innerWidth: 1024,