feat(extraction): same-file value-reference edges for impact analysis — 15 languages (#897)

Adds same-file value-reference edges (reader symbol → const/var it reads) so impact analysis catches a constant's same-file consumers, closing the 'change this table, break its readers' hole. 15 languages validated S/M/L on public OSS: TS/JS/tsx, Go, Python, Rust, Ruby, C, Java, C#, PHP, Scala, Kotlin, Swift, Dart, Pascal/Delphi (+ Svelte/Vue/Astro inherited). Edges-only — node count identical on/off; default ON, CODEGRAPH_VALUE_REFS=0 opts out.

src/extraction/languages/c-cpp.ts

@@ -110,6 +110,13 @@ export const cExtractor: LanguageExtractor = {
   nameField: 'declarator',
   bodyField: 'body',
   paramsField: 'parameters',
+  // A `const`/`static const` file-scope declaration carries a `type_qualifier`
+  // child reading "const" — extract those as `constant`, plain globals as
+  // `variable`.
+  isConst: (node) =>
+    node.namedChildren.some(
+      (c: SyntaxNode) => c.type === 'type_qualifier' && c.text === 'const'
+    ),
   getReturnType: extractCppReturnType,
   resolveTypeAliasKind: (node, _source) => {
     // C typedef: `typedef enum { ... } name;` or `typedef struct { ... } name;`