Add shellcheck CI workflow

.github/workflows/shellcheck.yml

@@ -0,0 +1,40 @@
+name: Shellcheck
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - '**.sh'
+      - '.shellcheckrc'
+      - '.github/workflows/shellcheck.yml'
+  pull_request:
+    branches: [ main ]
+    paths:
+      - '**.sh'
+      - '.shellcheckrc'
+      - '.github/workflows/shellcheck.yml'
+  workflow_dispatch:
+
+jobs:
+  shellcheck:
+    name: Shellcheck
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Run ShellCheck
+        uses: ludeeus/action-shellcheck@2.0.0
+        with:
+          severity: warning
+
+      - name: Verify shell scripts are executable
+        run: |
+          echo "Checking that all .sh files are executable..."
+          NON_EXECUTABLE=$(find . -type f -name "*.sh" ! -executable)
+          if [ -n "$NON_EXECUTABLE" ]; then
+            echo "ERROR: The following shell scripts are not executable:"
+            echo "$NON_EXECUTABLE"
+            exit 1
+          fi
+          echo "All shell scripts are executable"

.shellcheckrc

@@ -0,0 +1,8 @@
+# Shellcheck configuration for bc-github-actions
+# See: https://github.com/koalaman/shellcheck/wiki/Ignore
+
+# Don't follow sourced files - they may be generated or in other repos
+disable=SC1091
+
+# Allow referencing undefined variables set by Claude Code runtime
+disable=SC2154