Markdown diff blocks render without colors in the TUI #46475

Description

Markdown diff blocks appear without colors. Lines starting with + and - use the same text color instead of the theme's addition and deletion colors.

Plugins

None

OpenCode version

opencode2 v0.0.0-beta-18743 (also tested in regular opencode1, same issue)

Steps to reproduce

1. Start OpenCode and open a new conversation.

2. Ask the model to return this exact Markdown block:

   - removed line
   + added line
     unchanged line

3. Observe that the added and removed lines render without diff colors.

Expected: additions use the theme's added-line color and deletions use its removed-line color.

Screenshot and/or share link

Before	After #46480

Operating System

macOS

Terminal

Ghostty, Wezterm, iTerm2, Terminal