fix(tui): keep prompt border continuous in compact terminals

[Olusammytee]

Linked Issue\nCloses #438\n\n## Summary\n- use a continuous vertical border glyph at the prompt bottom-left corner\n- align the 1-row separator segment with the same border glyph when background elements are enabled\n- prevent the visual split seen in small terminal sizes\n\n## Testing\n- not run (visual TUI rendering fix)

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[kiloconnect]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

This PR makes two small cosmetic changes to the TUI prompt component, replacing the half-height vertical box-drawing character ╹ (BOX DRAWINGS LIGHT UP) with the full-height ┃ (BOX DRAWINGS HEAVY VERTICAL) for consistent border rendering. Both changes are in customBorderChars properties — one for bottomLeft and one for vertical. Clean and straightforward.

Files Reviewed (1 files)

• packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx

[Copilot]

Pull request overview

This PR fixes a visual issue where the vertical border near the input field appears split when the terminal window is resized to smaller heights. The fix ensures the border remains continuous by using the proper Unicode box drawing character throughout the prompt component.

Changes:

• Changed bottomLeft border character from "╹" to "┃" at the prompt bottom-left corner
• Changed vertical border character from "╹" to "┃" for the 1-row separator segment when background elements are enabled

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[Olusammytee]

Updated the PR description to include an explicit linked issue reference: Closes #438.

[Olusammytee]

Pushed a small cleanup follow-up: removed temporary inline comments from the two border-glyph lines while keeping behavior unchanged.