Move tree-sitter grammars to optionalDependencies for Windows compatibility

tree-sitter-kotlin doesn't ship prebuilt binaries for win32-x64, causing
npm install to fail on Windows without Visual Studio. All grammars are now
optional since the runtime already handles missing parsers gracefully.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@colbymchenry/codegraph",
-  "version": "0.4.3",
+  "version": "0.4.4",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@colbymchenry/codegraph",
-      "version": "0.4.3",
+      "version": "0.4.4",
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {