fix(cost): bill a session outside every workspace to its Linux account's user

A script's claude -p in a temp folder (the SG Flow eval runner strips the
pane's env) had no workspace, so its spend reached nobody's Today, the Users
page or a spend quota — ~$57 of a $74 day was missing from the status bar.

sessions.account records the Linux account a session ran as (the hook's
peer uid, else its folder for poller-made and old rows); a session no
workspace owns is owned by that account's user — a member's to them, the
host's to the admin ticked 'Owns this server's host account' (or the only
admin). Workspace ownership still wins.

server/openapi-extra/auth.js

@@ -790,6 +790,11 @@ const paths = {
         addWorkspaces: { type: "array", items: { type: "integer" } },
         removeWorkspaces: { type: "array", items: { type: "integer" } },
         signOut: { type: "boolean", enum: [true] },
+        hostAccount: {
+          type: "boolean",
+          description:
+            "An admin owns the host's Linux account: its sessions outside every workspace are billed to them (at most one; EBADROLE for a non-admin)",
+        },
         quota: { $ref: "#/components/schemas/UserQuotaSetting" },
       }),
       responses: {