fix(windows): suppress git check-ignore console popups during workspace polling

[Dimillian]

Motivation

• On Windows the app could spawn visible CMD windows when running git check-ignore during workspace polling, causing disruptive console popups.

Description

• Add std_command in src-tauri/src/shared/process_core.rs to construct a std::process::Command with CREATE_NO_WINDOW applied on Windows so synchronous subprocesses run hidden.
• Route the git check-ignore invocation in src-tauri/src/shared/git_ui_core/diff.rs through the new std_command helper so spawned git processes no longer open visible consoles.
• Preserve existing tokio_command behavior for async spawns and apply the same Windows-safe logic for synchronous command usage.

Testing

• Ran npm run typecheck which completed successfully.
• Ran cd src-tauri && cargo check which failed in this container due to a missing system glib-2.0 development package and is unrelated to the change.

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Codex Task

[Dimillian]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

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