fix(db): require better-sqlite3 ^12.4.1 so Node 24 gets the native backend (#203) (#216)

better-sqlite3 ^11.0.0 (latest 11.10.0) ships no prebuilt binary for
Node 24's ABI (node-v137) and predates Node 24, so every Node 24 install
silently fell back to the 5-10x-slower WASM backend. Bump to ^12.4.1 —
the first 12.x with the Node 24 prebuild — and raise the engines floor to
Node 20 (Node 18 is EOL and dropped from better-sqlite3 12.x prebuilds).

Verified on macOS Node 24.15.0 (ABI 137): prebuilt binary used with no
compiler (installs even with CC/CXX sabotaged), `codegraph init -i` shows
no WASM banner, and `codegraph status` reports Backend: native. 639/639
tests pass on Node 22.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package-lock.json

@@ -31,10 +31,10 @@
         "vitest": "^2.1.9"
       },
       "engines": {
-        "node": ">=18.0.0 <25.0.0"
+        "node": ">=20.0.0 <25.0.0"
       },
       "optionalDependencies": {
-        "better-sqlite3": "^11.0.0"
+        "better-sqlite3": "^12.4.1"
       }
     },
     "node_modules/@clack/core": {
@@ -992,15 +992,18 @@
       "optional": true
     },
     "node_modules/better-sqlite3": {
-      "version": "11.10.0",
-      "resolved": "https://registry.npmjs.org/better-sqlite3/-/better-sqlite3-11.10.0.tgz",
-      "integrity": "sha512-EwhOpyXiOEL/lKzHz9AW1msWFNzGc/z+LzeB3/jnFJpxu+th2yqvzsSWas1v9jgs9+xiXJcD5A8CJxAG2TaghQ==",
+      "version": "12.10.0",
+      "resolved": "https://registry.npmjs.org/better-sqlite3/-/better-sqlite3-12.10.0.tgz",
+      "integrity": "sha512-CyzaZRQKyHkB2ZInfTTl2nvT33EbDpjkLEbE8/Zck3Ll6O0qqvuGdrJ45HgtH+HykRg88ITY3AdreBGN70aBSQ==",
       "hasInstallScript": true,
       "license": "MIT",
       "optional": true,
       "dependencies": {
         "bindings": "^1.5.0",
         "prebuild-install": "^7.1.1"
+      },
+      "engines": {
+        "node": "20.x || 22.x || 23.x || 24.x || 25.x || 26.x"
       }
     },
     "node_modules/bindings": {