feat(llvm): Phase 132 - Fix PHI instruction ordering bug

Structural fix for LLVM backend PHI placement issue discovered in Phase 131.

Changes:
- Modified ensure_phi() to position PHI before existing instructions
- Enhanced setup_phi_placeholders() with debug mode
- Created phi_placement.py utility for validation
- Added test script for representative cases

Technical approach:
- PHI creation during setup (before block lowering)
- Explicit positioning with position_before(instrs[0])
- Debug infrastructure via NYASH_PHI_ORDERING_DEBUG=1

Design principles:
- PHI must be created when blocks are empty
- finalize_phis only wires, never creates
- llvmlite API constraints respected

Phase 132 complete. Ready for Phase 133 (ConsoleBox integration).

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

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

tools/test_phase132_phi_ordering.sh

@@ -0,0 +1,96 @@
+#!/bin/bash
+# Phase 132: Test PHI ordering fix
+# This script tests representative cases that had PHI ordering issues
+
+set -e
+
+cd "$(dirname "$0")/.."
+
+echo "=== Phase 132: PHI Ordering Test ==="
+echo ""
+
+# Enable debug mode for PHI ordering
+export NYASH_PHI_ORDERING_DEBUG=1
+export NYASH_CLI_VERBOSE=0
+
+# Test cases
+TEST_CASES=(
+    "local_tests/phase123_simple_if.hako"
+    "local_tests/phase123_while_loop.hako"
+    "apps/tests/loop_min_while.hako"
+    "apps/tests/joinir_if_select_simple.hako"
+)
+
+PASS=0
+FAIL=0
+RESULTS=()
+
+for test_case in "${TEST_CASES[@]}"; do
+    if [ ! -f "$test_case" ]; then
+        echo "⚠️  Skipping $test_case (not found)"
+        continue
+    fi
+
+    echo "---"
+    echo "Testing: $test_case"
+    echo ""
+
+    # Test with VM backend first (baseline)
+    echo "  VM backend..."
+    if ./target/release/hakorune --backend vm "$test_case" > /tmp/vm_out.txt 2>&1; then
+        VM_EXIT=$?
+        VM_OUTPUT=$(cat /tmp/vm_out.txt | grep -E "RC:|Exit code:" | tail -1)
+        echo "    ✅ VM: $VM_OUTPUT"
+    else
+        VM_EXIT=$?
+        echo "    ❌ VM failed with exit code $VM_EXIT"
+    fi
+
+    # Test with LLVM backend
+    echo "  LLVM backend..."
+    if NYASH_LLVM_USE_HARNESS=1 NYASH_LLVM_OBJ_OUT=/tmp/test_$$.o \
+       ./target/release/hakorune --backend llvm "$test_case" > /tmp/llvm_out.txt 2>&1; then
+        LLVM_EXIT=$?
+        LLVM_OUTPUT=$(cat /tmp/llvm_out.txt | grep -E "RC:|Exit code:" | tail -1)
+        echo "    ✅ LLVM: $LLVM_OUTPUT"
+
+        # Check for PHI ordering warnings
+        if grep -q "WARNING.*terminator" /tmp/llvm_out.txt; then
+            echo "    ⚠️  PHI ordering warning detected!"
+            RESULTS+=("⚠️  $test_case: PHI ordering warning")
+        else
+            RESULTS+=("✅ $test_case: PASS")
+            ((PASS++))
+        fi
+    else
+        LLVM_EXIT=$?
+        echo "    ❌ LLVM failed with exit code $LLVM_EXIT"
+
+        # Check error type
+        if grep -q "PHI" /tmp/llvm_out.txt; then
+            echo "    💥 PHI-related error!"
+        fi
+        RESULTS+=("❌ $test_case: FAIL (exit $LLVM_EXIT)")
+        ((FAIL++))
+    fi
+
+    echo ""
+done
+
+echo "==================================="
+echo "Phase 132 Test Results"
+echo "==================================="
+for result in "${RESULTS[@]}"; do
+    echo "$result"
+done
+echo ""
+echo "Summary: $PASS passed, $FAIL failed out of $((PASS + FAIL)) tests"
+echo ""
+
+if [ $FAIL -eq 0 ]; then
+    echo "🎉 All tests passed!"
+    exit 0
+else
+    echo "❌ Some tests failed"
+    exit 1
+fi