[plan] Migrate bundler and script registry to custom actions

[github-actions]

Objective

Complete the migration by updating the bundler and script registry systems to work with custom actions, and migrate all remaining JavaScript modules.

Context

This is the final integration step that connects all the pieces and completes the migration from embedded JavaScript to custom actions.

Approach

1. Update bundler.go to support custom action mode:
   • Skip inline bundling when using custom actions
   • Validate action references instead
2. Refactor script_registry.go:
   • Map script names to action paths
   • Support both inline (backward compat) and custom action modes
3. Migrate remaining JavaScript modules (all 200+):
   • Generate action.yml for all modules
   • Bundle JavaScript for each action
   • Update all references in compiler
4. Update make recompile to rebuild workflows with custom actions
5. Run full test suite and fix any issues
6. Update documentation and examples

Files to Modify

• pkg/workflow/bundler.go
• pkg/workflow/script_registry.go
• pkg/workflow/js.go (update all script references)
• All test files that reference inline scripts
• Makefile (update recompile target)
• AGENTS.md (update developer guide)

Acceptance Criteria

• All 200+ JavaScript modules are converted to custom actions
• Bundler works with custom action mode
• Script registry correctly maps names to action paths
• All tests pass (make test)
• All workflows recompile successfully (make recompile)
• Compiled workflow files are significantly smaller
• Documentation reflects new architecture
• Backward compatibility maintained for existing workflows
  Related to [plan] Refactor compiler to use custom actions for JavaScript code #5947

AI generated by Plan Command for #5946