tests: cover run_vulkan.sh release-path fallback behavior

[cursor]

Summary

Add deterministic regression coverage for scripts/run_vulkan.sh engine path resolution logic introduced in recent merged changes.

Risky behavior now covered

• Running scripts/run_vulkan.sh from repository scripts/ must execute engine binaries from sibling release/ directory.
• Running a copied run_vulkan.sh from inside release/ must still resolve and execute local engine binaries.
• Architecture-specific engine name selection (idtech3 vs idtech3.aarch64) must route correctly and preserve passthrough args.

Test files added/updated

• Added: tests/scripts/test_run_vulkan_path_resolution.sh
  • Creates isolated temp layouts for both execution contexts.
  • Uses fake engine stubs to assert selected executable path/name and forwarded arguments.
• Updated: CMakeLists.txt
  • Registers new CTest: test_run_vulkan_path_resolution (labels: unit;scripts;validation).

Why this materially reduces regression risk

Recent production behavior changed in a startup script used to launch the Vulkan client. Incorrect path resolution causes immediate startup failures in real deployments (repo-runner vs copied-script layouts). This test locks both supported layouts and architecture-dependent selection with deterministic assertions, preventing silent breakage in a high-blast-radius launch path.

Validation run

• tests/scripts/test_run_vulkan_path_resolution.sh scripts/run_vulkan.sh
• ctest -R test_run_vulkan_path_resolution --output-on-failure (from build-dbg)

Both passed in this environment.