Local file reads route through the storage backend when it serves the space

Marketplace file probes and start-up settings reads now go through the host storage backend instead of direct filesystem calls, each naming the storage space it wants, and fall back to ordinary file reads whenever the backend is absent, does not serve that space, or errors. A new start-up pass pre-reads managed-settings.json, its drop-in directory and the project and local settings layers, seeding parsed files and folder listings so the normal settings walk does not read them a second time. Every failure path is non-fatal, so the effect is fewer duplicate reads rather than any change in which settings win.