fix: stabilize TypeScript LSP startup

Seed new TypeScript LSP profiles with --stdio, validate that shared profiles keep the required flag, auto-add it for existing profiles in the sidecar runtime, and include recent stderr when a language server dies before completing a request. Add shared and sidecar regression coverage.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/shared/domain/tooling.ts

@@ -126,6 +126,11 @@ export function validateLspProfileDefinition(profile: LspProfileDefinition): str
     return `LSP profile "${profile.name}" needs at least one file extension.`;
   }
 
+  if (requiresTypeScriptLanguageServerStdio(profile.command)
+    && !normalizeStringArray(profile.args).some((arg) => arg.toLowerCase() === '--stdio')) {
+    return `LSP profile "${profile.name}" needs the "--stdio" argument.`;
+  }
+
   return undefined;
 }
 
@@ -168,6 +173,18 @@ function normalizeFileExtensions(fileExtensions: string[]): string[] {
   return normalizeStringArray(fileExtensions).map((value) => (value.startsWith('.') ? value : `.${value}`));
 }
 
+function requiresTypeScriptLanguageServerStdio(command: string): boolean {
+  const executableName = command
+    .trim()
+    .split(/[\\/]/)
+    .at(-1)
+    ?.toLowerCase();
+
+  return executableName === 'typescript-language-server'
+    || executableName === 'typescript-language-server.cmd'
+    || executableName === 'typescript-language-server.exe';
+}
+
 function normalizeStringArray(values?: ReadonlyArray<string>): string[] {
   if (!values) {
     return [];