Disable the process creation cursor animation by default

[OneBlue]

Summary of the Pull Request

This sets the STARTF_FORCEOFFFEEDBACK by default whenever we create new Windows processes.

This particularly useful during testing, since it prevents the cursor from jumping between "normal" and "process creation pending" state back and forth.

The flag is left untouched when creating interop processes, since this path can create interactive GUI processes on behalf of the user

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR changes the common Windows SubProcess helper to disable the process-creation cursor feedback animation by default (via STARTF_FORCEOFFFEEDBACK), while explicitly preserving the default cursor feedback behavior for interop-launched processes.

Changes:

• Extend wsl::windows::common::SubProcess to accept StartupFlags and default it to STARTF_FORCEOFFFEEDBACK.
• Plumb StartupFlags into STARTUPINFOEX::StartupInfo.dwFlags during process creation.
• Explicitly pass StartupFlags = 0 for interop process creation to avoid altering cursor feedback for potentially interactive GUI processes.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/windows/common/interop.cpp	Opts interop process creation out of the new default by passing StartupFlags = 0.
src/windows/common/SubProcess.h	Adds StartupFlags parameter (defaulting to STARTF_FORCEOFFFEEDBACK) and stores it on the class.
src/windows/common/SubProcess.cpp	Applies m_startupFlags into STARTUPINFOEX.StartupInfo.dwFlags when starting the process.

[benhillis]

Awesome, I did not know about this flag.