feat(phase32): L-2.1 Stage-1 UsingResolver JoinIR integration + cleanup

Phase 32 L-2.1 complete implementation:

1. Stage-1 UsingResolver main line JoinIR connection
   - CFG-based LoopForm construction for resolve_for_source/5
   - LoopToJoinLowerer integration with handwritten fallback
   - JSON snapshot tests 6/6 PASS

2. JoinIR/VM Bridge improvements
   - Simplified join_ir_vm_bridge.rs dispatch logic
   - Enhanced json.rs serialization
   - PHI core boxes cleanup (local_scope_inspector, loop_exit_liveness, loop_var_classifier)

3. Stage-1 CLI enhancements
   - Extended args.rs, groups.rs, mod.rs for new options
   - Improved stage1_bridge module (args, env, mod)
   - Updated stage1_cli.hako

4. MIR builder cleanup
   - Simplified if_form.rs control flow
   - Removed dead code from loop_builder.rs
   - Enhanced phi_merge.rs

5. Runner module updates
   - json_v0_bridge/lowering.rs improvements
   - dispatch.rs, selfhost.rs, modes/vm.rs cleanup

6. Documentation updates
   - CURRENT_TASK.md, AGENTS.md
   - Various docs/ updates

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/mir/mod.rs

@@ -30,6 +30,7 @@ pub mod join_ir; // Phase 26-H: 関数正規化IR（JoinIR）
 pub mod join_ir_ops; // Phase 27.8: JoinIR 命令意味箱（ops box）
 pub mod join_ir_runner; // Phase 27.2: JoinIR 実行器（実験用）
 pub mod join_ir_vm_bridge; // Phase 27-shortterm S-4: JoinIR → Rust VM ブリッジ
+pub mod join_ir_vm_bridge_dispatch; // Phase 30 F-4.4: JoinIR VM ブリッジ dispatch helper
 pub mod loop_form; // ControlForm::LoopShape の薄いエイリアス
 pub mod optimizer_passes; // optimizer passes (normalize/diagnostics)
 pub mod optimizer_stats; // extracted stats struct