Include desktop app logs in diagnostics (#1914)

* fix(diagnostics): include desktop app logs

Settings diagnostics now collect the Electron main-process log separately from daemon.log so desktop startup and environment-probe failures are included in app reports.

* refactor(desktop): share log tail reader

* fix(diagnostics): surface desktop app log read errors

* refactor(diagnostics): tighten desktop report API

packages/desktop/src/diagnostics/tail-file.ts

@@ -0,0 +1,21 @@
+import { readFileSync } from "node:fs";
+
+interface TailFileOptions {
+  throwOnReadError?: boolean;
+}
+
+export function tailFile(filePath: string, lines = 50, options: TailFileOptions = {}): string {
+  try {
+    const content = readFileSync(filePath, "utf-8");
+    return content.split("\n").filter(Boolean).slice(-lines).join("\n");
+  } catch (error) {
+    if (options.throwOnReadError && !isMissingFileError(error)) {
+      throw error;
+    }
+    return "";
+  }
+}
+
+function isMissingFileError(error: unknown): boolean {
+  return typeof error === "object" && error !== null && "code" in error && error.code === "ENOENT";
+}