refactor: unify clipboard copy flow across desktop/web/vscode runtimes (#458)

* fix: prevent copying incomplete diagnostics report

* refactoring: clipboard writes to unified cross-runtime fallback helper

packages/ui/src/lib/clipboard.ts

@@ -0,0 +1,39 @@
+export type ClipboardCopyResult =
+  | { ok: true; method: 'clipboard' | 'execCommand' }
+  | { ok: false; error: string };
+
+export async function copyTextToClipboard(text: string): Promise<ClipboardCopyResult> {
+  let clipboardError: string | null = null;
+
+  if (typeof navigator !== 'undefined' && navigator.clipboard?.writeText) {
+    try {
+      await navigator.clipboard.writeText(text);
+      return { ok: true, method: 'clipboard' };
+    } catch (error) {
+      clipboardError = error instanceof Error ? error.message : String(error);
+    }
+  }
+
+  if (typeof document !== 'undefined' && document.body) {
+    const textarea = document.createElement('textarea');
+    textarea.value = text;
+    textarea.setAttribute('readonly', '');
+    textarea.style.position = 'fixed';
+    textarea.style.top = '-1000px';
+    textarea.style.left = '-1000px';
+    document.body.appendChild(textarea);
+    textarea.select();
+    textarea.setSelectionRange(0, textarea.value.length);
+    const copied = document.execCommand('copy');
+    document.body.removeChild(textarea);
+
+    if (copied) {
+      return { ok: true, method: 'execCommand' };
+    }
+  }
+
+  return {
+    ok: false,
+    error: clipboardError ?? 'Clipboard access denied in current context',
+  };
+}

packages/ui/src/lib/debug.ts

@@ -5,6 +5,7 @@ import { useProjectsStore } from '@/stores/useProjectsStore';
 import { opencodeClient } from '@/lib/opencode/client';
 import { checkIsGitRepository } from '@/lib/gitApi';
 import { streamDebugEnabled } from '@/stores/utils/streamDebug';
+import { copyTextToClipboard as copyPlainTextToClipboard } from '@/lib/clipboard';
 
 export interface DebugMessageInfo {
   messageId: string;
@@ -373,13 +374,14 @@ export const debugUtils = {
     return JSON.stringify(report, null, 2);
   },
 
+  async copyTextToClipboard(text: string) {
+    return copyPlainTextToClipboard(text);
+  },
+
   async copyDiagnosticsReport() {
     const report = await this.buildDiagnosticsReport();
-    if (typeof navigator !== 'undefined' && navigator.clipboard) {
-      await navigator.clipboard.writeText(report);
-      return { ok: true, report } as const;
-    }
-    return { ok: false, report } as const;
+    const result = await this.copyTextToClipboard(report);
+    return { ...result, report } as const;
   },
 
    checkLastMessage() {