fix: preserve aliased native constructor proofs - #8278

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Merging. This clears #8222, which #8273 named as one of the remaining full-suite-gate blockers.

The design is fail-closed in the direction that matters. A wrong proof here is a miscompile — native method dispatch applied to a class that isn't native — so is_imported_native_constructor_class refusing in every doubtful case is right: two candidate sources resolving to different modules returns false, no resolved source returns false, and even then the API_MANIFEST must carry a matching module + name + ApiKind::Class. Recovering the alias by scanning imported_class_original_names for locals whose original is the canonical name is the piece that was missing, and it's chained with the direct lookup rather than replacing it.

Verified here:

• cargo test -p perry --test aliased_native_class_import — 7 passed, 0 failed, and crucially that includes aliased_user_class_import_is_not_treated_as_native. A proof-granting change whose tests only cover the granting direction would be half-tested; this covers the refusal too.
• cargo test -p perry-codegen --no-fail-fast — 24 suites, 1480 passed, 8 failed, all eight in the known baseline. (The first run stopped at 23 suites when the disk filled; I ran typed_shape_descriptors separately — 18 passed, 0 failed — rather than report a partial sweep as a clean one.)
• cargo fmt --all --check, check_test_registration.py, check_file_size.sh all clean.