fix: add bash execution guard to handle CI environments using sh

- Add bash version check at start of generated scripts
- Auto-reexecute with bash if running under sh/dash
- Prevents 'Illegal option -o pipefail' errors in GitHub Actions
- Ensures bash-specific features work regardless of CI shell environment

Author: Tom Brandenburg

src/generation/shell-generator.ts

@@ -362,6 +362,11 @@ function generateHeader(workflow: FlowshWorkflow, options: GenerationOptions): s
   const shell = options.shell === 'zsh' ? 'zsh' : 'bash';
 
   return `#!/bin/${shell}
+# Ensure we're running with bash (handle CI environments that might default to sh)
+if [ -z "$BASH_VERSION" ]; then
+  exec bash "$0" "$@"
+fi
+
 set -euo pipefail
 
 # ${name} - Generated by flowsh