Add WASM fallbacks for tree-sitter and SQLite, fix installer

Replace native tree-sitter with web-tree-sitter + tree-sitter-wasms for
universal cross-platform support. Add node-sqlite3-wasm as a fallback
when better-sqlite3 native bindings aren't available. Move better-sqlite3
and sqlite-vss to optionalDependencies so installs never fail.

Fix installer to use npx fallback when global npm install fails, so MCP
config, hooks, and quick-start instructions all work without the bare
codegraph command in PATH.

Fix tests: update schema version expectation, fix db test paths and
method names, extract MAX_OUTPUT_LENGTH as module constant, normalize
Windows path separators in import resolver.

src/index.ts

@@ -38,6 +38,7 @@ import {
   IndexResult,
   SyncResult,
   extractFromSource,
+  initGrammars,
 } from './extraction';
 import {
   ReferenceResolver,
@@ -60,7 +61,7 @@ export {
   CODEGRAPH_DIR,
 } from './directory';
 export { IndexProgress, IndexResult, SyncResult } from './extraction';
-export { detectLanguage, isLanguageSupported, getSupportedLanguages } from './extraction';
+export { detectLanguage, isLanguageSupported, getSupportedLanguages, initGrammars } from './extraction';
 export { ResolutionResult } from './resolution';
 export { EmbeddingProgress } from './vectors';
 export {
@@ -184,6 +185,7 @@ export class CodeGraph {
    * @returns A new CodeGraph instance
    */
   static async init(projectRoot: string, options: InitOptions = {}): Promise<CodeGraph> {
+    await initGrammars();
     const resolvedRoot = path.resolve(projectRoot);
 
     // Check if already initialized
@@ -253,6 +255,7 @@ export class CodeGraph {
    * @returns A CodeGraph instance
    */
   static async open(projectRoot: string, options: OpenOptions = {}): Promise<CodeGraph> {
+    await initGrammars();
     const resolvedRoot = path.resolve(projectRoot);
 
     // Check if initialized