refactor(phase62): Delete phi_input_collector.rs (-384 lines)

Phase 62前倒し: PhiInputCollectorの物理削除

Changes:
- Delete src/mir/phi_core/phi_input_collector.rs (-384 lines)
- Inline PhiInputCollector logic in json_v0_bridge/lowering/loop_.rs
  - sanitize: BTreeMap dedup + sort
  - optimize_same_value: check all inputs for same value
- Remove mod declaration in phi_core/mod.rs

Rationale:
- PhiInputCollector already inlined in Phase 59 (loopform_builder.rs)
- Last remaining usage was in JSON v0 Bridge
- Simple inline preserves exact behavior

Impact:
- -384 lines (Box + tests)
- No behavior change (inline equivalent)
- Build & test pass ✅

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

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

src/mir/phi_core/mod.rs

@@ -20,7 +20,7 @@ pub mod loop_var_classifier;
 
 // Phase 26-B: Box-First Refactoring
 // Phase 30 F-2.1: body_local_phi_builder 削除（LoopScopeShape で代替）
-pub mod phi_input_collector;
+// Phase 62: phi_input_collector 削除（インライン化完了）
 
 // Phase 26-C: Loop Snapshot Management
 // Phase 30 F-2.1: header_phi_builder 削除（JoinIR loop_step で代替）