Agent project-placement and the fetch/list grouping still resolved a
workspace from the agent's directory, even though every agent now
carries a workspaceId. Walk workspaceId -> workspace -> project instead:
an agent whose cwd is shared with or nested under another workspace now
groups under its own workspace, not a directory-prefix match. The fetch
path's placement map is keyed by workspace id, closing the
same-directory collision.
resolveWorkspaceIdForPath survives only at the archive-by-path boundary
(auto-archive-on-merge, the MCP archive tool), where a client passes a
bare worktree path with no id; renamed to match that role.