Add type alias and exported variable extraction

Extend extraction to index two additional categories of symbols
that were previously invisible:

1. Type aliases (e.g. `export type X = ...` in TypeScript,
   `type X` in Go, `type X = ...` in Rust, `typealias X` in Swift,
   `type_alias` in Kotlin). Adds `typeAliasTypes` to the
   LanguageExtractor interface with values for all 13 languages.

2. Exported variable declarations that aren't functions, including:
   - Zustand stores: `export const useX = create(...)`
   - XState machines: `export const xMachine = createMachine(...)`
   - Zod schemas: `export const schema = z.object(...)`
   - Config objects: `export const config = { ... }`
   - Constants: `export const MAX = 3`
   - Arrays: `export const NAMES = [...] as const`

   The extractExportedVariables() method is called when visiting
   export_statement nodes. It skips variable_declarator values that
   are already handled by functionTypes (arrow_function,
   function_expression) to avoid duplicate extraction.

Adds 11 new test cases (59 total extraction tests, 215 total).

Tested on production monorepo: nodes increased from 958 to 1,172
(+22%), with 109 new variable nodes and 105 new type_alias nodes.
Only 4 files remain at 0 nodes — all are re-export barrels or
ambient declaration files with no extractable symbols.

package-lock.json

@@ -1,12 +1,13 @@
 {
   "name": "@colbymchenry/codegraph",
-  "version": "0.2.6",
+  "version": "0.3.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@colbymchenry/codegraph",
-      "version": "0.2.6",
+      "version": "0.3.1",
+      "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
         "@xenova/transformers": "^2.17.0",