fix(tui): handle wide Bengali graphemes

[Blackman99]

Issue for this PR

Closes #46107

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Upgrades OpenTUI from 0.4.5 to 0.5.9 so terminals that use the unicode-wide profile measure complex Bengali graphemes correctly. The reported sample measured 12 cells before the upgrade and 18 cells after it, which prevents cumulative drift past the panel border.

The dependency and plugin peer versions were updated with the repository's upgrade-opentui script. A renderer regression test covers Bengali wrapping inside a border, a repeated render, terminal resize, and unchanged ASCII/CJK content.

How did you verify your code works?

• The renderer test fails on origin/dev because the width method falls back to unicode, then passes with OpenTUI 0.5.9 and unicode-wide.
• bun run test in packages/tui: 194 passed, 1 skipped.
• bun typecheck in packages/tui, packages/plugin, and packages/opencode.
• Pre-push bun turbo typecheck: 30/30 packages passed.
• bun install --frozen-lockfile.
• Prettier and oxlint on the new test: 0 warnings, 0 errors.

Screenshots / recordings

N/A — terminal-specific rendering is covered by exact wide and resized frame assertions.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR