Reuse global ACP config for remote agents

[wgqqqqq]

Summary

• Run remote ACP agents from the same saved ACP client config used locally, including custom commands, args, enabled state, permission mode, and env values.
• Replace the previous built-in-only remote command path with a shared remote shell renderer that loads common user toolchains (nvm, .local/bin, .cargo/bin, .npm-global/bin) and safely applies configured env before probing or starting the client.
• Add remote requirement probing and remote CLI installation through SSH, and clear cached remote capability snapshots after ACP config saves.
• Update the workspace ACP menu so remote workspaces show enabled local/global ACP clients only when that specific remote server probes as runnable, with forced refreshes for empty or stale snapshots.
• Rework the ACP settings page to show saved remote servers as first-class sections with availability summaries, per-agent CLI/ACP status, clearer issue labels, and context actions such as Install CLI, Configure ACP, Refresh Detection, and View Error.

Why

Remote ACP behavior was mixing two models: local settings controlled normal ACP clients, while remote workspaces used virtual built-in presets and fixed commands. That made local and remote color/status semantics diverge and made it unclear whether a remote server was using the user's actual ACP config.

This PR makes acpClients the single source of truth. Remote servers no longer get separate override controls in the settings UI; they reuse the global config and only maintain their own detected capability state.

User impact

• The same ACP agents configured locally are the agents considered for remote workspaces.
• Custom ACP clients can work remotely if their configured command is available on the remote server.
• Remote server cards now communicate available / total and concrete next steps instead of a generic config error.
• Saving ACP config invalidates remote capability cache so the frontend does not show stale remote availability.

Validation

• pnpm --dir src/web-ui run test:run
• cargo test -p bitfun-acp
• cargo check --workspace
• git diff --check