[FEATURE]: Better support remote/server-client use-cases from the CLI

[Killusions]

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

To support more advanced remote/server-client use-cases, as well as integrating it into CI containers and/or adding a control surface on top, a couple of key features are missing:

• Allow specifying --prompt in all remaining commands (attach, acp, serve and web (where a new session/chat is automatically started and the link to that specific session is printed / opened)). This allows having a control plane or system integration (think GitLab bot) and starting a session with a relevant prompt for the user.
• Allow attaching with --attach to an existing OpenCode server from other commands (acp, serve and web (where a proxy is opened to the existing server)). This allows for having a distributed architecture, like running the actual server inside of a container, but then proxying it for the user in a control plane with the correct CORS, etc. options. (optionally combined with --prompt to start a session).
• Allow attaching to session URLs in all commands (attach, acp, server and web) to continue with an existing session instead of just starting the server.
• Free win: add --session to the acp command since the logic was already there for --attach

Working and tested PR at #7340 , willing to do any adjustments if needed.

[github-actions]

This issue might be a duplicate of or closely related to existing issues. Please check:

• add --dir flag to opencode run --attach #7376: add --dir flag to opencode run --attach - related to --attach functionality
• [FEATURE]: Named Remote Connections with Session Origin Tracking #6461: [FEATURE]: Named Remote Connections with Session Origin Tracking - overlaps with remote connection tracking
• [FEATURE]: Adding Authentication to opencode server api #5256: [FEATURE]: Adding Authentication to opencode server api - server authentication feature
• [FEATURE]: SSH-based remote server connections to OpenCode Desktop #7790: [FEATURE]: SSH-based remote server connections to OpenCode Desktop - remote server connections
• [FEATURE]: OpenCode-Desktop Remote Workspace #5608: [FEATURE]: OpenCode-Desktop Remote Workspace - remote workspace support
• [Enhancement] Desktop app and terminal should connect to existing server instead of starting a new one when port is already in use #7629: [Enhancement] Desktop app and terminal should connect to existing server instead of starting a new one - connecting to existing servers
• [FEATURE]: opentui: Replace subcommands attach, spawn, thread with flags #3607: [FEATURE]: opentui: Replace subcommands attach, spawn, thread with flags - related to attach command redesign
• Unable to use --agent option when using run with --attach #8094: Unable to use --agent option when using run with --attach - attach command issues

Feel free to ignore if none of these address your specific case.

[Killusions]

I filed a working and tested PR at #7340 , willing to do any adjustments if needed