* fix(cli): use rundll32 instead of cmd.exe for Windows browser fallback in dashboard command
Extract resolveOpenCommand(platform, url) as an exported pure function so tests import the actual production code instead of duplicating logic.
The openFallback function in bin/cli/commands/dashboard.mjs used cmd /c start to open the dashboard URL on Windows, spawning an unnecessary cmd.exe process. Replaces with rundll32 url.dll,FileProtocolHandler which opens the URL directly through the Windows shell handler API without any shell wrapper.
Tests: 5 tests importing the actual resolveOpenCommand function, covering all platform branches (darwin, win32, linux) and URL pass-through. Changelog fragment included.
* chore: rename changelog fragment 7842->7844 to match actual PR number
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Co-authored-by: tientien17 <tientien17@users.noreply.github.com>
