test(pykotor): area layout deserialize errors and object roundtrip

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Description

Adds regression tests for recently merged headless area layout and JSON I/O: invalid saved data, impossible tile extension, and placed objects.

Type of Change

• ✅ Test addition or update

Package(s) Affected

• PyKotor (core library)

Risky behavior now covered

• extend_tile_from_wall / _best_adjacent_wall_hook: When the target tile template has no wall hook matching the active wall’s template id, layout extension must fail with a clear ValueError instead of silently misplacing geometry.
• area_layout_from_dict: Missing kitID in the kits map and invalid floor templateID overrides must raise predictable ValueErrors (bad hand-edited or merged layout JSON).
• Objects in layout JSON: AreaRoom.add_object data must round-trip through area_layout_to_dict / area_layout_from_dict with kit id, template id, and position preserved.

Test files added/updated

• Libraries/PyKotor/tests/test_area_layout.py — extended _layout_test_kit() with an OBJECT template for round-trip coverage; new tests for hook mismatch, missing kit, bad floor override, and object serialization.

Why these tests materially reduce regression risk

Indoor / module-design tooling depends on deterministic layout state and safe deserialization. Silent mis-linking of tiles or accepting corrupt JSON would corrupt walkmeshes and MDL placement downstream (area_layout_to_merged_bwm, area_layout_model_placements). These tests lock in explicit failure modes and prove the object list survives save/load, which was not previously asserted.

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Test Results

cd Libraries/PyKotor && uv run pytest --import-mode=importlib -m "not gui and not slow" tests/test_area_layout.py -v
# 8 passed

Also: uv run ruff check tests/test_area_layout.py and uv run ruff format tests/test_area_layout.py.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Related Issues

Regression coverage automation (cron); no specific issue.

Additional Notes

Tests are fully deterministic (synthetic TileKit fixtures, no disk or network). uv sync at workspace root can fail on unpublished optional deps; tests were run from Libraries/PyKotor with uv sync --extra dev per package README patterns.

AgentDecompile status: Skipped - test-only change, no game-engine or binary behavior :(