[kacy]

A generic body specialized in another module used the instantiating module's names. Its imports were the caller's, so a call from it into a third module's generic did not resolve, and a generic signature naming its own module's type picked up a same-named type in the caller. The emitter now uses the declaring module's imports while it emits a specialization, and the driver gives each module's emission the imports of the generic modules it depends on. The checker now types a generic call's signature in the declaring module.

A generic and a plain struct with one name in two modules are now kept apart. The pair is treated like two same-named generics, a module's own plain type shadows a foreign generic, and a generic impl no longer takes the plain struct's type id. Two modules that declare the same generic enum now compile, and each module's constructors and matches use its own declaration.

The std/algo workaround for the cross-module call is gone. Regression cases cover each shape, and docs/limitations.md drops the fixed entries.

Closes #1095