📚 Reorganize CLAUDE.md: slim down from 916 to 395 lines with proper doc links

- Keep essential information within 500 lines (now 395 lines)
- Maintain important syntax examples and development principles
- Move detailed information to appropriate docs files:
  - Development practices → docs/guides/development-practices.md
  - Testing guide → docs/guides/testing-guide.md
  - Claude issues → docs/tools/claude-issues.md
- Add proper links to all referenced documentation
- Balance between minimal entry point and practical usability

tools/build_llvm.sh

@@ -0,0 +1,69 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+if [[ "${NYASH_CLI_VERBOSE:-0}" == "1" ]]; then
+  set -x
+fi
+
+usage() {
+  cat << USAGE
+Usage: tools/build_llvm.sh <input.nyash> [-o <output>]
+
+Compiles a Nyash program with the LLVM backend to an object (.o),
+links it with the NyRT static runtime, and produces a native executable.
+
+Options:
+  -o <output>   Output executable name (default: app)
+
+Requirements:
+  - LLVM 18 development (llvm-config-18)
+  - NyRT static runtime (crates/nyrt)
+USAGE
+}
+
+if [[ $# -lt 1 ]]; then usage; exit 1; fi
+
+INPUT=""
+OUT="app"
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    -h|--help) usage; exit 0 ;;
+    -o) OUT="$2"; shift 2 ;;
+    *) INPUT="$1"; shift ;;
+  esac
+done
+
+if [[ ! -f "$INPUT" ]]; then
+  echo "error: input file not found: $INPUT" >&2
+  exit 1
+fi
+
+if ! command -v llvm-config-18 >/dev/null 2>&1; then
+  echo "error: llvm-config-18 not found (install LLVM 18 dev)." >&2
+  exit 2
+fi
+
+echo "[1/4] Building nyash (feature=llvm) ..."
+LLVM_SYS_180_PREFIX=$(llvm-config-18 --prefix) cargo build --release --features llvm >/dev/null
+
+echo "[2/4] Emitting object (.o) via LLVM backend ..."
+OBJ="nyash_llvm_temp.o"
+rm -f "$OBJ"
+LLVM_SYS_180_PREFIX=$(llvm-config-18 --prefix) ./target/release/nyash --backend llvm "$INPUT" >/dev/null || true
+if [[ ! -f "$OBJ" ]]; then
+  echo "error: object not generated: $OBJ" >&2
+  exit 3
+fi
+
+echo "[3/4] Building NyRT static runtime ..."
+( cd crates/nyrt && cargo build --release >/dev/null )
+
+echo "[4/4] Linking $OUT ..."
+cc "$OBJ" \
+  -L crates/nyrt/target/release \
+  -Wl,--whole-archive -lnyrt -Wl,--no-whole-archive \
+  -lpthread -ldl -lm -o "$OUT"
+
+echo "✅ Done: $OUT"
+echo "   (runtime requires nyash.toml and plugin .so per config)"
+