test(joinir): Phase 129 P2 - add post-if return var fixture + VM smoke

- Add phase129_if_only_post_if_return_var_min.hako
  - Pattern: x=1; if flag==1 { x=2 }; print(x)
  - Tests join_k continuation env merge

- Add phase129_if_only_post_if_return_var_vm.sh
  - Expected output: 2 (x updated in then branch)
  - Dev-only: NYASH_JOINIR_DEV=1 HAKO_JOINIR_STRICT=1

Note: Currently passes via fallback path (non-Normalized)
P1 implementation (join_k materialization) is next step

tools/smokes/v2/profiles/integration/apps/phase129_if_only_post_if_return_var_vm.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+# Phase 129: If-only Post-If Return Var (Normalized join_k, VM)
+#
+# Verifies that join_k continuation properly merges env after if:
+# - x=1; flag=1; if flag==1 { x=2 }; return x
+# - join_k receives env_phi (x=2 from then, x=1 from else)
+# - Returns x=2 (flag=1 fixed)
+# - Dev-only: NYASH_JOINIR_DEV=1 HAKO_JOINIR_STRICT=1
+
+source "$(dirname "$0")/../../../lib/test_runner.sh"
+source "$(dirname "$0")/../../../lib/output_validator.sh"
+export SMOKES_USE_PYVM=0
+require_env || exit 2
+
+PASS_COUNT=0
+FAIL_COUNT=0
+RUN_TIMEOUT_SECS=${RUN_TIMEOUT_SECS:-10}
+
+echo "[INFO] Phase 129: If-only Post-If Return Var (Normalized join_k, VM)"
+
+# Test 1: phase129_if_only_post_if_return_var_min.hako
+echo "[INFO] Test 1: phase129_if_only_post_if_return_var_min.hako"
+INPUT="$NYASH_ROOT/apps/tests/phase129_if_only_post_if_return_var_min.hako"
+
+set +e
+OUTPUT=$(timeout "$RUN_TIMEOUT_SECS" env \
+  NYASH_DISABLE_PLUGINS=1 \
+  HAKO_JOINIR_STRICT=1 \
+  NYASH_JOINIR_DEV=1 \
+  "$NYASH_BIN" --backend vm "$INPUT" 2>&1)
+EXIT_CODE=$?
+set -e
+
+if [ "$EXIT_CODE" -eq 124 ]; then
+  echo "[FAIL] hakorune timed out (>${RUN_TIMEOUT_SECS}s)"
+  FAIL_COUNT=$((FAIL_COUNT + 1))
+elif [ "$EXIT_CODE" -eq 0 ]; then
+  # Phase 129: expect x=2 (print(x) after if with x=2)
+  EXPECTED="2"
+  if validate_numeric_output 1 "$EXPECTED" "$OUTPUT"; then
+    echo "[PASS] Output verified: 2 (exit code: $EXIT_CODE)"
+    PASS_COUNT=$((PASS_COUNT + 1))
+  else
+    echo "[INFO] output (tail):"
+    echo "$OUTPUT" | tail -n 50 || true
+    FAIL_COUNT=$((FAIL_COUNT + 1))
+  fi
+else
+  echo "[FAIL] hakorune failed with exit code $EXIT_CODE"
+  echo "[INFO] output (tail):"
+  echo "$OUTPUT" | tail -n 50 || true
+  FAIL_COUNT=$((FAIL_COUNT + 1))
+fi
+
+echo "[INFO] PASS: $PASS_COUNT, FAIL: $FAIL_COUNT"
+
+if [ "$FAIL_COUNT" -eq 0 ]; then
+  test_pass "phase129_if_only_post_if_return_var_vm: All tests passed"
+  exit 0
+else
+  test_fail "phase129_if_only_post_if_return_var_vm: $FAIL_COUNT test(s) failed"
+  exit 1
+fi