ACP unstable_listSessions only returns sessions for the current project

[remorses]

Description

unstable_listSessions in the ACP agent calls sdk.session.list() which is scoped to the current project via Instance.project.id. When running opencode acp from / (or any non-git directory), the project ID resolves to "global", so sessions from actual git projects are never returned.

The global session list endpoint (GET /experimental/session) backed by Session.listGlobal() already exists and queries SQLite across all projects, but the ACP agent doesn't use it.

Steps to reproduce

1. Have sessions in multiple git projects
2. Start ACP server from /: opencode acp --cwd /
3. Call unstable_listSessions({ cwd: "/" })
4. Only sessions with projectID === "global" are returned — sessions from git projects are missing

Expected behavior

unstable_listSessions should return sessions from all projects, using the existing experimental.session.list endpoint.

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• [BUG] Zed ACP registry mode shows stale Recent sessions (unscoped /session) #16137: Same root cause — ACP session listing is scoped to the current project/cwd, so sessions from other projects are not returned when running opencode acp from a non-git or different directory.