File sync: detection for unrecognized working copies and alternate roots is built in but disabled

What

File sync is the step that brings a local folder's files into a cloud session. This build adds two related pieces of detection, and both rely on a detector function, I0, that returns null every time. A companion function, vr, always returns !1 (false). As a result, neither piece can trigger:

• The unrecognized working copy check: a new helper, mO, would make the sync-folder check return unrecognized_working_copy and make the working-copy test in Tf return true early. New messages come with it: "File sync is not available for this launch (...)" and "starting a session from local files is switched off, so this cloud session starts without this folder's files". Because I0 returns null, mO is always false.
• The alternate root lookup: JGn always returns null, and Ot always uses its fallback, so XR(e) behaves like Ro(e) and YH(e) like qW(e). The root and readability checks built around Ict, a hash comparison against hVn(), cannot be reached.

Why

Nothing changes for you in this build. File sync behaves as it did, and the new "File sync is not available" message cannot appear yet. The code is ready to be switched on in a later build.