fix(windows): keep temporary pastes out of clipboard history

[badigit]

Before Submitting This PR

Please confirm you have done the following:

• I have searched existing issues and pull requests (including closed ones) to ensure this isn't a duplicate
• I have read CONTRIBUTING.md

If this is a feature or change that was previously closed/rejected:

• I have explained in the description below why this should be reconsidered
• I have gathered community feedback (link to discussion below)

Human Written Description

On W11 , the "don't modify clipboard" option was still filling my Win+V history with duplicates and empty entries. I use clipboard history all the time, so this was really annoying. This fix keeps pasting fast without changing or polluting the clipboard history.

Related Issues/Discussions

Related: #1356

This issue was closed because clipboard-based paste was assumed to have no way to avoid Windows clipboard-history entries. Windows exposes registered clipboard formats specifically for excluding a clipboard transaction from monitoring, history, and cloud sync, which makes a Windows-specific fix possible without changing the paste mechanism.

Community Feedback

The original report and reproduction are in #1356. No separate discussion has been opened because this is a bug fix for the existing Don't Modify Clipboard behavior, not a new feature.

Testing

• Built the Windows x64 production application, MSI, and NSIS installer in the existing GitHub Actions workflow: https://github.com/badigit/Handy/actions/runs/29920434836
• The workflow's Windows runtime audit installed both packages, verified bundled runtime DLLs, and launched handy.exe --list-devices successfully.
• Manually tested the unsigned Windows build on Windows 11 with clipboard history enabled. Clipboard-mode transcriptions remained fast, the previous clipboard content was restored, and repeated pastes did not add transcription or blank entries to Win+V history.
• Added unit coverage for CF_DIB byte layout, invalid RGBA lengths, and empty image dimensions.
• An independent read-only review found no remaining blocking issues after removing test-only version/workflow changes and extending clipboard-open retries to approximately 475 ms.

Screenshots/Videos (if applicable)

Not included. The behavior is observable directly in the Windows Win+V clipboard-history panel; reproduction steps are documented in #1356.

AI Assistance

• No AI was used in this PR
• AI was used (please describe below)

If AI was used:

• Tools used: OpenAI Codex
• How extensively: Codex investigated the Windows clipboard behavior, implemented most of the patch and tests, prepared the cloud build, and performed an independent read-only review. The contributor manually tested the resulting Windows build.