ci: give the Windows test leg a 50-minute budget

The Windows leg runs the same suite ~1.6x slower than macOS. On the base
branch it already took 34m40s of the flat 35-minute budget, and with this
PR's added tests it was cancelled at the limit mid-run (no failures).
Linux and macOS keep 35 minutes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018tncU7u7FK48tubFNA12UQ

Author: claude

.github/workflows/ci.yml

@@ -237,7 +237,9 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
-    timeout-minutes: 35
+    # Windows runs the same suite ~1.6x slower than macOS: on the base
+    # branch it already took 34m40s of a flat 35m budget.
+    timeout-minutes: ${{ matrix.os == 'windows-latest' && 50 || 35 }}
     steps:
       - name: Checkout
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2