Load package dependencies of interfaces

[jeet-dekivadia]

Summary

• queue newly discovered package and interface trees for recursive dependency discovery
• add interface-imported packages to shallow compilation without recursively walking discovered modules
• add a regression fixture where a module depends on an interface that imports its payload type from a package

Correctness

The originating tree is always inspected. Discovered documents are always added to the shallow dependency set, but only package and interface syntax trees are queued for another discovery step. For the regression graph, the walk reaches interface_consumer -> transitive_if -> transitive_pkg. A module discovered beneath another file is not queued, so the loader does not recursively follow the design hierarchy.

Fixes #349

Remote Linux validation

• git diff --check
• uv run pre-commit run --all-files
• cmake --preset clang-release -DSLANG_CI_BUILD=ON
• cmake --build build/clang-release -j2
• ctest --test-dir build/clang-release --output-on-failure --no-tests=error -j2
• uv venv
• source .venv/bin/activate
• uv sync
• pytest tests/system/ --binary build/clang-release/bin/slang-server

[AndrewNolte]

This will result in a whole design being loaded in shallow compilation; we don't want this.

[jeet-dekivadia]

Thanks for catching this. I narrowed the queue so discovered packages and interfaces are inspected recursively, while discovered modules are still added as shallow dependencies but are not queued. That keeps the interface-imported package case working without following the design hierarchy. I reran the Linux configure, build, CTest, and system-test lane successfully.