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_pattern2_parse_number.hako

@@ -0,0 +1,31 @@
+// Phase 163: Test _parse_number from JsonParserBox (Pattern2 with break)
+// Simulates: loop(digit_pos >= 0) { num_str += ch; p++; break if non-digit }
+
+static box Main {
+  main(args) {
+    local num_str = "12345abc"
+    local i = 0
+    local digits = "0123456789"
+    local result = ""
+
+    // Simulate _parse_number: collect digits until non-digit
+    loop(i < num_str.length()) {
+      local ch = num_str.substring(i, i + 1)
+      local digit_pos = digits.indexOf(ch)
+
+      // Exit on non-digit
+      if digit_pos < 0 {
+        break
+      }
+
+      // Append digit
+      result = result + ch
+      i = i + 1
+    }
+
+    print("Input: " + num_str)
+    print("Parsed: " + result)
+    print("Stopped at index: " + ("" + i))
+    return 0
+  }
+}