fix: use bash shell for electron prebuild step on Windows

The version normalization script uses bash syntax ([[ ]], =~) but had no
shell: directive, defaulting to pwsh on Windows runners which cannot
parse it.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: TimelordUK

.github/workflows/prebuild.yml

@@ -223,6 +223,7 @@ jobs:
         npm ls node-abi node-gyp
 
     - name: Prebuild Electron binaries
+      shell: bash
       run: |
         VERSION="${{ matrix.electron }}"
         # Only append .0.0 if version doesn't already contain a dot (i.e., is just a number like 30, 31)