feat(tui): add tui.attach config and --attach flag to connect to existing server

[R44VC0RP]

Summary

This essentially allows you to be able to have a default server set for the TUI so that you don't manually have to run opencode attach <server> every single time.

It also adds an additional option in the /status that allows you to see what server you are currently attached too.

This is what it looks like when it is connected to its own spawned server:

And this is what it looks like when it is connected to a server in the attach json:

• Adds tui.attach config option to automatically connect TUI to an existing OpenCode server
• Adds --attach <url> CLI flag for ad-hoc server attachment
• Shows "Attached to {url}" in status dialog when connected to external server
• Falls back to spawning a new worker if the configured server is unavailable

Usage

Via config (opencode.json):

{
  "tui": {
    "attach": "http://opencode.local"
  }
}

Via CLI flag:

opencode --attach http://localhost:4096

Testing

Tested locally by running a server on opencode.local and verifying the TUI attaches without spawning a new worker.

[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.

[github-actions]

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

Based on the search results, I found one potentially related PR:

Related PR:

• PR fix(cli): skip local agent validation in attach mode #8154: fix(cli): skip local agent validation in attach mode
  • This PR deals with "attach mode" functionality and may be related to the attach feature being added in PR feat(tui): add tui.attach config and --attach flag to connect to existing server #9683, though it appears to focus on CLI validation rather than the TUI config/flag implementation.

No true duplicate PRs were found. PR #9683 appears to be the first implementation of the tui.attach config option and --attach CLI flag for connecting to existing servers.