Fix: TUI single-line paste cursor position

[Octane0411]

Fix: TUI single-line paste cursor position

Description

This PR fixes a bug where pasting single-line text in the TUI prompt would incorrectly move the cursor to the end of the input buffer, instead of placing it immediately after the pasted text.

Issue

Fixes #7210

Changes

• Removed input.gotoBufferEnd() from the onPaste handler in opencode/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx.

Verification

• Verified that input.gotoBufferEnd() was the cause of the cursor jump.
• The default behavior of the textarea component handles cursor positioning correctly for pasted text.
• Retained markDirty() and requestRender() to ensure UI updates correctly after paste.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found

[Octane0411]

Hi @thdxr, this is a small fix for the cursor jumping issue reported in #7210.

Root Cause:
I've confirmed this was a regression introduced in #6070 (commit 2806f24). The input.gotoBufferEnd() call was added to handle resizing but inadvertently forces the cursor to the end for all paste operations.

Fix:
My change removes the unnecessary cursor jump while preserving the layout update logic (markDirty / requestRender), ensuring the textarea still resizes correctly without disrupting the cursor position.

Demo
Before (Bug)

Kapture.2026-01-08.at.16.41.12.mp4

After (Fixed)

Kapture.2026-01-08.at.16.43.25.mp4

Ready for review when you have a chance. Thanks!