Preserve block tools when selecting blocks

[JeremyZeng77]

Summary

• Keeps block-compatible tools active when selecting a different block.
• Preserves Paint Terrain, Wall Tool, and Ground Plane Tool during block material changes.
• Still deactivates tools that are not block-compatible before switching the selected block.

Addresses #123

Verification

• git diff --check
• npm run build (passes with existing repository warnings about missing mediapipe source map, lint warnings, and bundle size)

Bounty / payment

If this PR is accepted for the bounty/open-source contribution program, PayPal is preferred: https://paypal.me/Jeremytsangchina

Backup payout option: USDT TRC20 TWupTAoFjxR2VmqUUvzhfmUwXVZR6Kvz1Y

[vercel]

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[JeremyZeng77]

Local verification completed for this change: \git diff --check\ passed and \
pm run build\ completed successfully. The Vercel status appears blocked by the team authorization page rather than by a build failure.