test(regression): CI JSON progress and BIF-sliced MDL reads

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Description

Adds focused regression tests for two recently merged high-risk areas: JSON export progress reporting under CI-like environment variables, and binary MDL loading when the resource lives at a non-zero offset inside a larger buffer (BIF / chitin slice semantics).

Type of Change

• ✅ Test addition or update

Package(s) Affected

• PyKotor (core library)

Risky behavior now covered

• _supports_live_progress in resource_json: When CI or GITHUB_ACTIONS is set to a truthy string, live \r progress is disabled even if stderr claims to be a TTY, so log-based assertions and aggregators still see percentage milestones via logger.info.
• MDLBinaryReader offset handling: Reading the same binary MDL from a padded buffer with offset/size (simulating a BIF entry) must match reading the standalone file—guards against double-counting offset+12 and bogus seeks.

Test files added/updated

• Libraries/PyKotor/tests/test_resource_json_progress_regressions.py (new)
• Libraries/PyKotor/tests/resource/formats/test_mdl_bif_slice_offset.py (new)

Why these tests materially reduce regression risk

• JSON export: A subtle CI-only behavior change can silently drop progress from structured logs while still “working” in the terminal; explicit env-matrix tests fail fast if someone removes or weakens the CI guard.
• MDL from archives: Wrong slice math corrupts geometry or fails parsing for every MDL pulled from chitin.key / BIFs; comparing slice vs file is a minimal end-to-end proof without depending on full models.bif roundtrips.

Testing

Command (from Libraries/PyKotor, uv with dev extra):

QT_QPA_PLATFORM=offscreen uv run python -m pytest --rootdir=/workspace/Libraries/PyKotor --import-mode=importlib -m "not gui and not slow" tests/test_resource_json_progress_regressions.py tests/resource/formats/test_mdl_bif_slice_offset.py -v

Result: 5 passed (0.13s). Tests are deterministic (temp env via monkeypatch, in-repo binary fixture).

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

Related to recent fixes on resource_json CI progress and MDLBinaryReader BIF offset handling.