feat(joinir): Phase 164 Pattern3 (If-Else PHI) validation complete

- Created 4 representative test cases for Pattern3 patterns:
  * test_pattern3_if_phi_no_break.hako - Core Pattern3 (if-else PHI, no break/continue)
  * test_pattern3_skip_whitespace.hako - Pattern3+break style (routed to Pattern2)
  * test_pattern3_trim_leading.hako - Pattern3+break style (routed to Pattern2)
  * test_pattern3_trim_trailing.hako - Pattern3+break style (routed to Pattern2)

- Validated Pattern3_WithIfPhi detection:
  * Pattern routing: Pattern3_WithIfPhi MATCHED confirmed
  * JoinIR lowering: 3 functions, 20 blocks → 8 blocks (successful)
  * [joinir/freeze] elimination: Complete (no errors on any test)

- Clarified pattern classification:
  * Pattern3_WithIfPhi handles if-else PHI without break/continue
  * Loops with "if-else PHI + break" are routed to Pattern2_WithBreak
  * Break takes priority over if-else PHI in pattern detection

- Cumulative achievement (Phase 162-164):
  * Pattern1: 6 loops working ✅
  * Pattern2: 5 loops working ✅
  * Pattern3 (no break): 1 loop working ✅
  * Pattern3+break (as Pattern2): 3 loops working ✅
  * Total: 15 loops covered, zero [joinir/freeze] errors

- Updated CURRENT_TASK.md with Phase 164 section and findings

Next: Phase 165 Pattern4 (continue) validation

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

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

tools/selfhost/test_pattern1_simple.hako

@@ -0,0 +1,17 @@
+// Phase 162: Simplest Pattern1 test (no ArrayBox/objects)
+// Just accumulate a counter in a simple loop
+
+static box Main {
+  main(args) {
+    local i = 0
+    local sum = 0
+
+    loop(i < 5) {
+      sum = sum + i
+      i = i + 1
+    }
+
+    print("Sum: " + ("" + sum))
+    return 0
+  }
+}