build: add fail-fast: false to CI matrix

Ensure both Python 3.12 and 3.13 jobs always run to completion
even if one fails.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 2 people

.github/workflows/main.yml

@@ -6,6 +6,7 @@ jobs:
   unittest:
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         python-version: ['3.12', '3.13']
     steps: