feat(opencode): add transparent TUI background option

[theabecaster]

Summary

• add tui.transparent_background config option
• respect transparent backgrounds in the TUI theme + root container

Testing

• not run (local build only)

Fixes #8399

[github-actions]

Hey! Your PR title Add transparent TUI background option doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

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

Potential Duplicate Found

PR #5657: feat: toggle transparent background

• feat: toggle transparent background #5657

This PR appears to be directly related - it's implementing a toggle for transparent background in the TUI. Your PR (#8403) implements the same feature with a tui.transparent_background config option. These are likely addressing the same issue and should be reviewed together to avoid duplicate work.

[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.

[rekram1-node]

Let's avoid adding new config options, you can toggle it via command panel instead, also can u provider before and after screenshots please?

[theabecaster]

Let's avoid adding new config options, you can toggle it via command panel instead, also can u provider before and after screenshots please?

done new config removed, you can now open the command palette (Ctrl+P) and select “Enable transparent background” or “Disable transparent background.” It’s saved in your local KV, so it persists between runs.

Screen shots:
disabled:

enabled: