docs: Phase 196 Implementation Results documentation

Updated documentation with Phase 196 completion details:

1. phase196-select-bug-fix.md:
   - Added "Implementation Results" section with fix details
   - Before/After code examples
   - Complete test results (all patterns PASS)
   - Reference to phase196-select-bug-analysis.md

2. joinir-architecture-overview.md:
   - Added Select expansion invariant to InstructionRewriter section
   - "PHI inputs must use remapper.remap_instruction() remapped ValueIds"
   - "InstructionRewriter only remaps block IDs, not ValueIds"

3. CURRENT_TASK.md:
   - Marked Phase 196 as complete with summary
   - Added Phase 197 as next candidate (JsonParser deployment)

All Phase 196 documentation now complete.

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/development/current/main/joinir-architecture-overview.md

@@ -276,6 +276,10 @@ JoinIR ラインで守るべきルールを先に書いておくよ：
     - continuation 関数（k_exit）をスキップし、Return → exit ブロック Jump に変換。
     - `JoinFragmentMeta.expr_result` と exit_bindings をヘッダ PHI 経由で収集し、`exit_phi_inputs` / `carrier_inputs` を復活させた（SSA‑undef 修正済み）。
     - tail call を Branch/Jump に書き換えつつ、LoopHeaderPhiInfo に latch 入力を記録する。
+  - **Select 展開の不変条件（Phase 196）**:
+    - PHI の入力 ValueId は必ず `remapper.remap_instruction()` で remap 済みの MIR ValueId を使用。
+    - InstructionRewriter では ValueId の二重 remap を行わない（block ID のみ remap）。
+    - 詳細: [phase196-select-bug-analysis.md](./phase196-select-bug-analysis.md)
 
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