Fix toolbar selection persistence through block changes

[keilogic]

Fixes #123

Summary:

• Block selection was deactivating every active toolbar tool except the terrain sculpt tool.
• Added a small preserve list for block-driven tools so Paint Terrain, Wall Tool, and Ground Tool stay active when switching blocks.
• Kept the change scoped to BlockToolsSidebar.js.

Validation:

• npm install --no-package-lock - passed when preparing the patch
• npm run build - passed with existing upstream warnings when preparing the patch
• git diff --check origin/main...HEAD - passed

Note:

• This issue is currently labeled Improvement, not BOUNTY, so I am submitting it as a normal contribution. If HYTOPIA treats it as eligible under the paid bounty system, payment can be sent here: https://www.paypal.com/paypalme/aogkft

[vercel]

@keilogic is attempting to deploy a commit to the Hytopia Team on Vercel.

A member of the Team first needs to authorize it.