## Summary
- Auto-discover signtool.exe from Windows SDK instead of relying on
`SIGNTOOL_PATH` repository variable
- Add `/debug` flag to signtool for better diagnostics during signing
failures
- Remove `SIGNTOOL_PATH` env var from the electron-builder step since
it's now set dynamically

#skip-bugbot

## Test plan
- Verify the release workflow runs successfully on Windows runners
- Check that signtool.exe is found from the Windows SDK directory
- Confirm signing output includes debug information

🤖 Generated with [Claude Code](https://claude.com/claude-code)
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<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Automatically discover the Windows SDK SignTool in the release workflow
and set its path via GITHUB_ENV, removing the need for the SIGNTOOL_PATH
repo variable. Adds /debug to SignTool for clearer diagnostics during
signing.

- **Refactors**
- Auto-find x64 signtool.exe from the Windows SDK and export
SIGNTOOL_PATH dynamically.
  - Add /debug to signWithParams for better logging.
  - Remove SIGNTOOL_PATH from the electron-builder step.

<sup>Written for commit e667e794ac6b4c13bf34ab2943182fd22de26da0.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>