Help me contribute to Mega Man X. Task: code-screen-transform — Test screen coordinate transforms. Kit: 2026-09-10.4.

Read INSTRUCTIONS.md, tasks.json and the inputs listed for this task (or the equivalent sections of AI-CONTEXT.en.md). Clone the public code at https://github.com/davidluky/megaman-x-engine and read its AGENTS.md, CONTRIBUTING.md and docs/reference-data.md. Use a task branch and keep the kit outside the checkout. The default core/contracts build needs no ROM; full gameplay requires separate inputs.

Objective: Inspect screen_transform and existing coverage. Propose a direct contract for invalid dimensions, letterboxing and points outside the internal viewport.
Acceptance: Test deterministic mathematics only, without opening a window. Register the CMake target and describe cases and CTest results.
Limits: Read existing contracts before adding another. Do not change scaling, camera or gameplay coordinates to accommodate the test.

Work on this task now. Cite the exact fields, paths or timestamps you used. Do not invent findings or test results. Save output/report.json using templates/report.json; add report.md if helpful. Run tools/check_submission.py --report output/report.json only if you can execute Python locally; otherwise mark it not_run and return the report text. A structural PASS is not proof of gameplay correctness. Return the reviewed report or a small scoped patch for human review; do not send, push or publish automatically.
