A missing module build now fails loudly instead of compiling quietly

Until now, when a module's prebuilt assemblies could not be fetched — the registry did not advertise the package for this framework build, served no bytes for the lane, or shipped a bundle with nothing in it — the mesh logged a line and compiled the module locally. On a production portal that fallback hides a distribution failure: the install "succeeds", slowly, and the real problem (no bundle was ever baked for that lane) surfaces days later as something else entirely.

Deployments can now set Modules:RequirePrebuilt: true. On such a mesh, every one of those misses fails the install immediately with one clear message naming the package, the registry, the framework identity and architecture the bundle is missing for, and the fix — publish or rebake the bundle for that lane. Nothing compiles. The adoption ledger still records every miss, and an empty bundle found at boot is reported as an error naming the same fix.

The default is unchanged: meshes that do not opt in — local and dev meshes, CI's disposable meshes, the bake itself — keep the compile fallback, which remains correct wherever bundles are not expected to exist.