Feature: Add VB.NET language support (tree-sitter approach)

[Michael2150]

Add native VB.NET tree-sitter extraction

Supersedes #170 (closed — never applied).

The original PR depended on an external companion project (codegraph-roslyn) that invoked Roslyn as a subprocess and required shipping platform-specific native binaries alongside the npm package. That approach doesn't fit the self-contained model codegraph uses for every other language, so this PR rebuilds VB.NET support from scratch using a bundled tree-sitter grammar instead.

What gets extracted

Node kinds: class, module, struct, interface, enum, enum_member, method (Sub/Function, constructors via Sub New), property, field, constant, namespace, import

Edges: calls (invocations), contains, imports, instantiates

VB.NET-specific handling:

• Module blocks extracted as module kind with isStatic: true (VB.NET Modules are implicitly static sealed types, not regular classes)
• Structure blocks extracted as struct kind with full member nesting (fields, properties, methods)
• Inherits/Implements lines are filtered out — the grammar misparsed them as field_declaration nodes; the extractor detects and drops them
• Sub New extracted as a method named New (constructor)
• Shared modifier maps to isStatic: true
• Friend modifier maps to 'internal' visibility
• Async modifier maps to isAsync: true
• Method signatures: (params) As ReturnType for Functions, (params) for Subs

Files changed

• src/types.ts — 'vbnet' added to LANGUAGES
• src/extraction/grammars.ts — .vb extension mapping, 'vbnet': 'VB.NET' display name, vendored wasm path
• src/extraction/languages/vbnet.ts (new) — full VB.NET extractor: type classification, visibility, modifiers, signature generation, namespace/module/struct/const handling via visitNode
• src/extraction/languages/index.ts — vbnetExtractor registered
• src/extraction/wasm/tree-sitter-vbnet.wasm (new) — bundled grammar (see provenance below)
• __tests__/extraction.test.ts — smoke test covering all node kinds in one pass
• CHANGELOG.md — entry under [Unreleased]
• README.md — VB.NET listed as supported

src/extraction/wasm/tree-sitter-vbnet.wasm — provenance

Built from tree-sitter-vb-dotnet@0.1.9 (by codeant-ai).
The npm package ships grammar source only (no prebuilt WASM), so the file was compiled locally:

npm pack tree-sitter-vb-dotnet          # download tarball
tar -xzf tree-sitter-vb-dotnet-0.1.9.tgz -C /tmp/vb-grammar
cd /tmp/vb-grammar/package
npm install -g tree-sitter-cli          # tree-sitter 0.26.9
tree-sitter build --wasm               # downloads wasi-sdk, compiles parser.c -> .wasm
cp tree-sitter-vb_dotnet.wasm <repo>/src/extraction/wasm/tree-sitter-vbnet.wasm

Testing

Validated against the codegraph-roslyn fixture repo (7 VB.NET files, 20 C# files):

• 146 VB.NET nodes extracted across all 7 files, zero parse errors
• All node kinds present: class (14), method (58), field (21), property (17), enum (2), enum_member (8), struct (2), module (1), interface (3), namespace (8), import (5)
• 164 edges: contains (139), calls (18), imports (5), instantiates (2)
• C#/VB parity across parallel fixture files (Animals, AsyncPatterns, EventSystem, ImportAliases all within +/-1 node)