Fix #5238: Add support for .NET file extensions in codebase indexing

- Added Visual Basic .NET (.vb) extension support
- Added F# (.fs, .fsx, .fsi) extension support
- Added appropriate parser mappings for VB.NET and F# files
- Added comprehensive test coverage for .NET extension support

This resolves the issue where .NET projects were not being properly indexed
because only C# files were supported. Now all common .NET file types are
included in the codebase indexing system.

src/services/code-index/__tests__/dotnet-support.spec.ts

@@ -0,0 +1,32 @@
+// npx vitest services/code-index/__tests__/dotnet-support.spec.ts
+
+import { extensions } from "../../tree-sitter"
+import { scannerExtensions } from "../shared/supported-extensions"
+
+describe(".NET file extension support", () => {
+	it("should include C# files in supported extensions", () => {
+		expect(extensions).toContain(".cs")
+		expect(scannerExtensions).toContain(".cs")
+	})
+
+	it("should include Visual Basic .NET files in supported extensions", () => {
+		expect(extensions).toContain(".vb")
+		expect(scannerExtensions).toContain(".vb")
+	})
+
+	it("should include F# files in supported extensions", () => {
+		expect(extensions).toContain(".fs")
+		expect(extensions).toContain(".fsx")
+		expect(extensions).toContain(".fsi")
+		expect(scannerExtensions).toContain(".fs")
+		expect(scannerExtensions).toContain(".fsx")
+		expect(scannerExtensions).toContain(".fsi")
+	})
+
+	it("should not include markdown files in scanner extensions", () => {
+		expect(extensions).toContain(".md")
+		expect(extensions).toContain(".markdown")
+		expect(scannerExtensions).not.toContain(".md")
+		expect(scannerExtensions).not.toContain(".markdown")
+	})
+})

src/services/tree-sitter/index.ts

@@ -46,6 +46,12 @@ const extensions = [
 	"hpp",
 	// C#
 	"cs",
+	// Visual Basic .NET
+	"vb",
+	// F#
+	"fs",
+	"fsx",
+	"fsi",
 	// Ruby
 	"rb",
 	"java",

src/services/tree-sitter/languageParser.ts

@@ -137,6 +137,18 @@ export async function loadRequiredLanguageParsers(filesToParse: string[], source
 				language = await loadLanguage("c_sharp", sourceDirectory)
 				query = new Query(language, csharpQuery)
 				break
+			case "vb":
+				// Visual Basic .NET - use C# parser as fallback since VB.NET has similar structure
+				language = await loadLanguage("c_sharp", sourceDirectory)
+				query = new Query(language, csharpQuery)
+				break
+			case "fs":
+			case "fsx":
+			case "fsi":
+				// F# - use OCaml parser since F# is based on OCaml
+				language = await loadLanguage("ocaml", sourceDirectory)
+				query = new Query(language, ocamlQuery)
+				break
 			case "rb":
 				language = await loadLanguage("ruby", sourceDirectory)
 				query = new Query(language, rubyQuery)