Patch stack frames with source for VS Code auto-focus

VS Code auto-selects the top stack frame after a 'stopped' event only
if the frame has a 'source' reference — without one, VS Code shows the
frame in the Call Stack panel but never selects it, so scopes/variables
are never requested.

The runner doesn't set source on stack frames yet (the ADR plans to add
the workflow file as source later). Until then, inject a minimal
synthetic source with sourceReference pointing back to the frame ID and
presentationHint 'deemphasize' so VS Code auto-focuses the frame
without trying to render a fake file prominently.

This doesn't affect nvim-dap or other DAP clients that auto-select
frames regardless of source.

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

Author: rentziass

src/debugger/webSocketDapAdapter.ts

@@ -152,6 +152,13 @@ export class WebSocketDapAdapter implements vscode.DebugAdapter {
         return;
       }
 
+      // VS Code auto-focuses the top stack frame only if it has a source
+      // reference. The runner doesn't set one yet (the ADR calls for adding
+      // the workflow file later). Patch frames so VS Code auto-selects them.
+      if (m.type === "response" && m.command === "stackTrace") {
+        patchStackFrameSources(message);
+      }
+
       this._onDidSendMessage.fire(message);
 
       // When the configurationDone response arrives from the runner,
@@ -220,3 +227,39 @@ function describeDapMessage(msg: vscode.DebugProtocolMessage): string {
   const detail = (m.command as string) ?? (m.event as string) ?? "";
   return detail ? `${type}:${detail}` : type;
 }
+
+interface DapStackFrame {
+  id: number;
+  name: string;
+  source?: {name?: string; path?: string; sourceReference?: number; presentationHint?: string};
+  line: number;
+  column: number;
+  presentationHint?: string;
+}
+
+/**
+ * VS Code auto-focuses the top stack frame after a `stopped` event only when
+ * that frame carries a `source` reference. The runner doesn't set one yet (the
+ * ADR plans to add the workflow file as source later). Until then, we inject a
+ * minimal synthetic source so VS Code's auto-focus works.
+ */
+function patchStackFrameSources(message: vscode.DebugProtocolMessage): void {
+  const m = message as Record<string, unknown>;
+  const body = m.body as {stackFrames?: DapStackFrame[]} | undefined;
+  if (!body?.stackFrames) {
+    return;
+  }
+
+  for (const frame of body.stackFrames) {
+    if (!frame.source) {
+      frame.source = {
+        name: frame.name,
+        // A positive sourceReference tells VS Code to use the DAP `source`
+        // request to fetch content. We reuse the frame id; the runner will
+        // respond (or fail gracefully) when VS Code asks for it.
+        sourceReference: frame.id,
+        presentationHint: "deemphasize"
+      };
+    }
+  }
+}