test(smoke): Phase 283 P0 - Add VM/LLVM smoke tests + doc update

- VM smoke: phase283_p0_loop_if_phi_vm.sh (checks sum=9 output)
- LLVM smoke: phase283_p0_loop_if_phi_llvm.sh (checks Result: 0, exit=0)
- Documentation: Update phase-283 README with LLVM harness notes
  - LLVM harness suppresses program stdout
  - VM shows stdout, LLVM checks exit code only

Both tests verified: ✅ PASS

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

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

tools/smokes/v2/profiles/integration/apps/phase283_p0_loop_if_phi_llvm.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Phase 283 P0: Pattern3 loop_if_phi fix (LLVM harness backend)
+# Tests: loop(i <= 5) with if-else phi (sum += odd numbers)
+set -euo pipefail
+
+HAKO_PATH="apps/tests/loop_if_phi.hako"
+
+# LLVM harnessはstdoutを抑制するため、exit=0 (Result: 0) で判定
+EXPECTED_EXIT=0
+
+NYASH_LLVM_USE_HARNESS=1 $HAKORUNE_BIN --backend llvm "$HAKO_PATH"
+actual_exit=$?
+
+if [[ $actual_exit -eq $EXPECTED_EXIT ]]; then
+    echo "✅ phase283_p0_loop_if_phi_llvm: PASS (exit=$actual_exit)"
+    exit 0
+else
+    echo "❌ phase283_p0_loop_if_phi_llvm: FAIL (expected=$EXPECTED_EXIT, got=$actual_exit)"
+    exit 1
+fi

tools/smokes/v2/profiles/integration/apps/phase283_p0_loop_if_phi_vm.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+# Phase 283 P0 - Pattern3 loop_if_phi fix (VM backend)
+# Tests: loop(i <= 5) with if-else phi (sum += odd numbers)
+
+HAKO_FILE="apps/tests/loop_if_phi.hako"
+BACKEND="vm"
+
+# Expected: [Console LOG] sum=9
+EXPECTED_OUTPUT="sum=9"
+
+ACTUAL_OUTPUT=$(./target/release/hakorune --backend "$BACKEND" "$HAKO_FILE" 2>&1 | grep -o 'sum=[0-9]*')
+
+if [ "$ACTUAL_OUTPUT" = "$EXPECTED_OUTPUT" ]; then
+    echo "✅ PASS: phase283_p0_loop_if_phi_vm"
+    exit 0
+else
+    echo "❌ FAIL: phase283_p0_loop_if_phi_vm"
+    echo "Expected:"
+    echo "$EXPECTED_OUTPUT"
+    echo "Got:"
+    echo "$ACTUAL_OUTPUT"
+    echo "---Full output (last 80 lines):---"
+    ./target/release/hakorune --backend "$BACKEND" "$HAKO_FILE" 2>&1 | tail -n 80
+    exit 1
+fi