Phase 50 implements the Loop Frontend Binding layer that maps
actual loop variables to JoinIR Frontend's expected names (i, acc, n).
## Changes
- Add loop_frontend_binding.rs module with:
- LoopFrontendBinding struct for variable mapping
- for_print_tokens() and for_array_filter() factory methods
- generate_local_declarations() for JSON v0 format
- rename_body_variables() for out → acc renaming
- Integrate binding with cf_loop_joinir_impl:
- Create binding based on function name
- Inject i/acc/n Local declarations into JSON v0
- Use correct JoinIR Frontend type names (Int/Var/Method)
## Limitations Found
JoinIR Frontend doesn't support:
- Field access (me.tokens) - blocks print_tokens
- NewBox (new ArrayBox()) - blocks array_filter
These will be addressed in Phase 51.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
