fix(theme): add selectedListItemText to orng themes for button text visibility

[ThanhNguyxn]

Summary

Fixes #6849

The orng and lucent-orng themes were missing the selectedListItemText property, causing button text in permission dialogs to be invisible.

Problem

When using the orng theme, the permission dialog buttons have invisible text because:

• Button background uses primary color (orange #EC5B2B)
• Button text defaults to background color (black #0a0a0a in dark mode)
• Black text on orange background is hard to read, and in some terminal configurations appears completely invisible

Solution

Added explicit selectedListItemText values to both theme files:

• Dark mode: #0a0a0a (black) - provides good contrast on orange background
• Light mode: #ffffff (white) - provides good contrast on lighter orange

Files Changed

• packages/opencode/src/cli/cmd/tui/context/theme/orng.json
• packages/opencode/src/cli/cmd/tui/context/theme/lucent-orng.json

Testing

Manual testing required:

1. Set theme to orng
2. Trigger a permission dialog (e.g., file write operation)
3. Verify button text is now visible