feat(joinir): Phase 286 P3.2 - Pattern5 Plan line (loop(true) + early exit)

- Pattern5InfiniteEarlyExitPlan (Return/Break variants)
- extract_pattern5_plan() for loop(true) literal only
- normalize_pattern5_return(): 5 blocks CFG (header→body→found/step)
- normalize_pattern5_break(): 6 blocks CFG with carrier PHI
- NormalizationPlanBox exclusion for Pattern5-style loops
- Fixtures: phase286_pattern5_{return,break}_min.hako
- quick smoke 154/154 PASS

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

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

apps/tests/phase286_pattern5_break_min.hako

@@ -0,0 +1,16 @@
+// Phase 286 P3.2: Pattern5 infinite loop with break
+// Tests: loop(true) with if (i == 3) { break } and carrier update
+// Expected: 3 (sum = 0 + 1 + 1 + 1 = 3 for i = 0, 1, 2)
+
+static box Main {
+  main() {
+    local i = 0
+    local sum = 0
+    loop(true) {
+      if (i == 3) { break }
+      sum = sum + 1
+      i = i + 1
+    }
+    return sum
+  }
+}

apps/tests/phase286_pattern5_return_min.hako

@@ -0,0 +1,14 @@
+// Phase 286 P3.2: Pattern5 infinite loop with early return
+// Tests: loop(true) with if (i == 3) { return 7 }
+// Expected: 7
+
+static box Main {
+  main() {
+    local i = 0
+    loop(true) {
+      if (i == 3) { return 7 }
+      i = i + 1
+    }
+    return 0
+  }
+}