fix(hooks): replace DETACHED_PROCESS with CREATE_NO_WINDOW on Windows

[hopstreax]

Summary

Fixes #2253.

On Windows, Graphify's Git hook launcher started the background rebuild using DETACHED_PROCESS together with python.exe. Since python.exe is a console-subsystem executable, this caused Windows to open a new console window during every background rebuild triggered by post-commit and post-checkout hooks.

This change replaces DETACHED_PROCESS with CREATE_NO_WINDOW while preserving the existing detached background execution behavior by keeping:

• CREATE_NEW_PROCESS_GROUP
• CREATE_BREAKAWAY_FROM_JOB (best-effort)

The POSIX launch path (start_new_session=True) is unchanged.

Changes

• Replace the Windows DETACHED_PROCESS creation flag with CREATE_NO_WINDOW in the hook launcher.
• Update the launcher comment to reflect the new Windows creation flag.
• Update the corresponding regression test to verify the generated launcher contains CREATE_NO_WINDOW.

Why this approach?

The hook launcher introduced in #1161 was designed to replace the previous nohup-based implementation with a cross-platform Python launcher. This change preserves those original design goals:

• Git commits return immediately.
• Background rebuilds continue independently.
• Cross-platform behavior remains unchanged.
• No dependency on shell-specific utilities.

CREATE_NO_WINDOW suppresses the unwanted console window while retaining the existing process-group behavior through CREATE_NEW_PROCESS_GROUP and the existing best-effort CREATE_BREAKAWAY_FROM_JOB.

Validation

Tested on Windows by:

• Installing Git hooks with graphify hook install
• Performing Git commits
• Verifying no console window appears
• Verifying commits complete immediately
• Verifying the background rebuild still executes
• Verifying rebuild logs are still written
• Verifying graph.json, graph.html, and GRAPH_REPORT.md are regenerated

Also updated and ran the relevant hook regression test to validate the generated launcher uses the expected Windows creation flags.

[safishamsi]

Thanks @hopstreax. Shipped in v0.9.29 (cherry-picked to v8 to preserve authorship). Closed-unmerged here, but it's in the release: https://github.com/Graphify-Labs/graphify/releases/tag/v0.9.29