ci: remove continue-on-error from test job

Make CI test failures blocking so that broken builds are not silently
ignored. Previously the test matrix had `continue-on-error: true`, which
allowed failing tests to pass the overall workflow.

Co-Authored-By: Claude (fennec-v7-fast) <noreply@anthropic.com>

Author: maxisbey

.github/workflows/shared.yml

@@ -32,7 +32,6 @@ jobs:
     name: test (${{ matrix.python-version }}, ${{ matrix.dep-resolution.name }}, ${{ matrix.os }})
     runs-on: ${{ matrix.os }}
     timeout-minutes: 10
-    continue-on-error: true
     strategy:
       matrix:
         python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]