feat(mir/llvm): Phase 273 P0-P1 DomainPlan→CorePlan + LLVM arg fix

Phase 273 P0-P1: Two-layer plan architecture
- DomainPlan: Pattern-specific knowledge (ScanWithInit)
- CorePlan: Fixed vocabulary (Seq, Loop, If, Effect, Exit)
- ValueId references only (String expressions forbidden)
- Pipeline: Extractor→Normalizer→Verifier→Lowerer

New plan/ module:
- mod.rs: Type definitions, SSOT spec
- normalizer.rs: DomainPlan→CorePlan + ID allocation
- verifier.rs: V1-V6 invariant checks (fail-fast)
- lowerer.rs: CorePlan→MIR (pattern-agnostic)

LLVM fix (ChatGPT):
- function_lower.py: Fix argument reference bug
- Phase 258 index_of_string now PASS on LLVM backend

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

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

tools/smokes/v2/profiles/integration/apps/phase258_p0_index_of_string_llvm_exe.sh

@@ -2,18 +2,25 @@
 # Phase 258 P0: index_of_string (dynamic needle) - LLVM backend
 set -euo pipefail
 
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/../../../../../.." && pwd)"
+HAKORUNE_BIN="${HAKORUNE_BIN:-$PROJECT_ROOT/target/release/hakorune}"
+
 HAKO_PATH="apps/tests/phase258_p0_index_of_string_min.hako"
 
 # Test: "hello world".index_of_string("world") → 6
 EXPECTED_EXIT=6
 
-NYASH_LLVM_USE_HARNESS=1 $HAKORUNE_BIN --backend llvm "$HAKO_PATH"
+set +e
+NYASH_LLVM_USE_HARNESS=1 "$HAKORUNE_BIN" --backend llvm "$PROJECT_ROOT/$HAKO_PATH"
 actual_exit=$?
+set -e
 
 if [[ $actual_exit -eq $EXPECTED_EXIT ]]; then
     echo "✅ phase258_p0_index_of_string_llvm_exe: PASS (exit=$actual_exit)"
     exit 0
 else
     echo "❌ phase258_p0_index_of_string_llvm_exe: FAIL (expected=$EXPECTED_EXIT, got=$actual_exit)"
+    echo "    Hint: build LLVM harness via: cargo build --release --features llvm"
     exit 1
 fi