feat(phi): Phase 25.1 - BTreeMap移行 (21ファイル、80%決定性達成)

## 修正内容

### Core MIR/PHI (5ファイル)
- builder.rs: variable_map, value_types, value_origin_newbox
- context.rs: 3つのマップ
- loop_builder.rs: 3箇所
- loop_snapshot_manager.rs: snapshot マップ
- loop_snapshot_merge.rs: 2箇所

### MIR関連 (4ファイル)
- function.rs: FunctionMetadata.value_types
- resolver.rs: CalleeResolverBox
- guard.rs: CalleeGuardBox
- loop_common.rs: apply_increment_before_continue

### JSON Bridge (5ファイル)
- json_v0_bridge/lowering.rs
- json_v0_bridge/lowering/expr.rs
- json_v0_bridge/lowering/if_else.rs
- json_v0_bridge/lowering/merge.rs
- json_v0_bridge/lowering/try_catch.rs
- json_v0_bridge/mod.rs

### Printer & Providers (4ファイル)
- printer.rs, printer_helpers.rs
- host_providers/mir_builder.rs
- backend/mir_interpreter/handlers/extern_provider.rs

### Tests (3ファイル)
- phi_core/conservative.rs
- tests/json_program_loop.rs
- tests/mir_stage1_using_resolver_verify.rs (2テスト有効化)

## テスト結果
- mir_stage1_using_resolver_resolve_with_modules_map_verifies: 80%成功率
- 完全な決定性は未達成 (HashMap 86箇所、HashSet 63箇所が残存)

🐱 Generated with Claude Code

src/mir/builder/phi_merge.rs

@@ -8,7 +8,7 @@
 
 use super::{BasicBlockId, MirBuilder, ValueId};
 use crate::mir::MirInstruction;
-use std::collections::HashMap;
+use std::collections::BTreeMap; // Phase 25.1: 決定性確保
 
 /// PHI Merge Helper - 統一PHI挿入ロジック（Conservative戦略）
 ///
@@ -158,9 +158,9 @@ impl<'a> PhiMergeHelper<'a> {
     /// Ok(()) on success, Err(String) on failure
     pub fn merge_all_vars(
         &mut self,
-        pre_if_snapshot: &HashMap<String, ValueId>,
-        then_map_end: &HashMap<String, ValueId>,
-        else_map_end_opt: &Option<HashMap<String, ValueId>>,
+        pre_if_snapshot: &BTreeMap<String, ValueId>, // Phase 25.1: BTreeMap化
+        then_map_end: &BTreeMap<String, ValueId>, // Phase 25.1: BTreeMap化
+        else_map_end_opt: &Option<BTreeMap<String, ValueId>>, // Phase 25.1: BTreeMap化
         skip_var: Option<&str>,
     ) -> Result<(), String> {
         // Use Conservative strategy from conservative module