Report tool-card clipboard failures and clear stale copy feedback #72

Part of #2.

Tool-card Copy buttons silently ignore clipboard failures and can keep saying Copied after streamed output changes.

Make input and output copying report pending, successful and failed attempts independently. Keep failure feedback visible while the section is collapsed, allow an explicit retry, and discard feedback for superseded text or attempts. Preserve complete plain-text copying from shortened previews and diff inputs.

Verify clipboard rejection, retry, pending operations and streaming updates in component tests, plus a real Electron failure/retry interaction with screenshots at desktop and minimum window sizes.