test(joinir): fix Phase 33-3.2 test flakiness by unifying env-dependent tests

Phase 33-3.2 test stabilization:
- Unified 4 env-dependent tests into 1 (test_if_select_pattern_matching)
- Eliminated race condition from parallel test execution
- All 5 tests now pass consistently (5/5 stable PASS)

Before: 8 tests (flaky 7-8/8 due to env var race)
After: 5 tests (stable 5/5, no flakiness)

Test coverage maintained:
- Simple pattern lowering (env ON)
- Local pattern lowering (env ON)
- Disabled by default (env OFF)
- Wrong function name filter (env ON)
- 4 verify tests (env-independent, kept separate)

Documentation:
- Updated TASKS.md with test flake resolution notes
- Updated docs/private submodule to 81ec67f

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

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

src/tests/mir_joinir_if_select.rs

@@ -124,15 +124,17 @@ mod tests {
         }
     }
 
+    /// Phase 33-3: 統合パターンマッチングテスト（env 競合回避）
+    ///
+    /// env 変数を触る4つのテストを1つにまとめて、並列実行でのレースを防ぐ。
+    /// 順番に: simple/local/disabled/wrong_name を確認する。
     #[test]
-    fn test_if_select_simple_pattern() {
-        // Set environment variable for this test
+    fn test_if_select_pattern_matching() {
+        // ==== 1. Simple pattern (env ON) ====
         std::env::set_var("NYASH_JOINIR_IF_SELECT", "1");
 
         let func = create_simple_pattern_mir();
         let entry_block = func.entry_block;
-
-        // Try to lower to JoinIR
         let result = try_lower_if_to_joinir(&func, entry_block, true);
 
         assert!(
@@ -153,18 +155,9 @@ mod tests {
             panic!("Expected JoinInst::Select, got {:?}", result);
         }
 
-        // Clean up
-        std::env::remove_var("NYASH_JOINIR_IF_SELECT");
-    }
-
-    #[test]
-    fn test_if_select_local_pattern() {
-        std::env::set_var("NYASH_JOINIR_IF_SELECT", "1");
-
+        // ==== 2. Local pattern (env ON) ====
         let func = create_local_pattern_mir();
         let entry_block = func.entry_block;
-
-        // Try to lower to JoinIR
         let result = try_lower_if_to_joinir(&func, entry_block, true);
 
         assert!(
@@ -185,18 +178,11 @@ mod tests {
             panic!("Expected JoinInst::Select, got {:?}", result);
         }
 
-        std::env::remove_var("NYASH_JOINIR_IF_SELECT");
-    }
-
-    #[test]
-    fn test_if_select_disabled_by_default() {
-        // Ensure environment variable is NOT set
+        // ==== 3. Disabled by default (env OFF) ====
         std::env::remove_var("NYASH_JOINIR_IF_SELECT");
 
         let func = create_simple_pattern_mir();
         let entry_block = func.entry_block;
-
-        // Should return None when disabled
         let result = try_lower_if_to_joinir(&func, entry_block, false);
 
         assert!(
@@ -205,19 +191,13 @@ mod tests {
         );
 
         eprintln!("✅ If/Select lowering correctly disabled by default");
-    }
 
-    #[test]
-    fn test_if_select_wrong_function_name() {
+        // ==== 4. Wrong function name (env ON) ====
         std::env::set_var("NYASH_JOINIR_IF_SELECT", "1");
 
-        // Create function with wrong name (not IfSelectTest.*)
         let mut func = create_simple_pattern_mir();
         func.signature.name = "WrongName.test/1".to_string();
-
         let entry_block = func.entry_block;
-
-        // Should return None for non-IfSelectTest functions
         let result = try_lower_if_to_joinir(&func, entry_block, true);
 
         assert!(
@@ -227,6 +207,7 @@ mod tests {
 
         eprintln!("✅ Function name filter working correctly");
 
+        // Clean up
         std::env::remove_var("NYASH_JOINIR_IF_SELECT");
     }