feat: add requiresModuleSystem package option in Lake#13646
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This PR adds a new package configuration option `requiresModuleSystem`. When a package sets it to `true`, Lake emits a warning whenever a module from another package imports any of its modules without itself using the module system (i.e., without a `module` header). This lets package authors signal that their API is designed for the visibility and elaboration semantics of the module system. The check lives in `fetchImportInfo` and runs once per import after resolving the providing module(s); the disambiguation case (multiple packages providing the same module name) warns if any provider has the flag set.
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This PR adds a companion configuration option `silenceRequiresModuleSystemWarning` that lets a package opt out of the warning emitted by Lake when it imports modules from a `requiresModuleSystem` dependency without using the module system. This is intended for packages that have knowingly decided not to migrate to the module system yet. The flag is honored by `fetchImportInfo` via a new `silenceWarning` parameter threaded from the importing module's package configuration.
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This PR adds a new Lake package option
requiresModuleSystem. When a package sets it totrue, Lake emits a warning whenever a non-module-system file (one without amoduleheader) imports a module of the package, both from downstream consumers and from non-module files within the package itself. This signals that the package's API expects the visibility and elaboration semantics of the module system. A companion optionallowNonModuleslets an importing package opt out of these warnings, declaring that it knowingly mixes non-module-system files with module-system dependencies.