[viralcodex]

Summary

• Upgrade Core, React, and Solid development and peer dependencies from 0.6.6 to 0.8.1 and refresh the lockfile.
• Update the README requirement to OpenTUI 0.8.x.
• Preserve pane dragging when OpenTUI reports the split container as the mouse-down target, using the existing coordinate lookup.

Testing

• Bun 1.3.14 and Node.js 26.4.0.
• Frozen-lockfile installation.
• Lint, formatting, and typecheck passed.
• All 44 existing tests passed, including React and Solid adapter tests.
• Build and compiled-package rendering passed on Bun and Node.js with experimental FFI.
• Confirmed the original nested-content drag regression passes without modifying tests.

Existing uncommitted work in the main checkout is excluded from this PR.