test(tslpatcher): strengthen merge artifact and INI section coverage

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Description

Adds regression tests for recent diff/TSLPatcher merge and INI serialization behavior: default merge-conflict artifact location, JSON report consistency with on-disk files, unknown merge conflict policy defaulting, and triple duplicate GFF modifier section names in generated INI.

Type of Change

• ✅ Test addition or update

Package(s) Affected

• PyKotor (core library)

Risky behavior now covered

• Merge conflict artifact layout: default tslpatchdata/merge_conflicts/ when --merge-conflict-output is omitted; custom path still works.
• conflicts.json contract: paths in JSON point to real files; resource name, policy, and mod paths are preserved (catches merge/report drift).
• Conflict policy normalization: invalid or missing policy string falls back to mod-a so CLI typos do not flip merge behavior silently.
• INI section uniqueness: three modifiers sharing one logical section name produce section, section_1, section_2 with no duplicate [...] headers (TSLPatcher parser compatibility).

Test files added/updated

• Libraries/PyKotor/tests/tslpatcher/diff/test_diff_tslpatcher.py

Why these tests materially reduce regression risk

They lock the merge-to-TSLPatcher workflow’s on-disk debugging artifacts and INI shape to behavior mod authors and patch tools depend on. A bad default path or broken JSON would waste user time without catching it in CI; duplicate INI section names can break TSLPatcher/HoloPatcher readers.

Testing

Ran (environment without uv; same paths as AGENTS.md):
PYTHONPATH=Libraries/PyKotor/src:Libraries/Utility/src:Tools/KotorDiff/src python3 -m pytest --import-mode=importlib Libraries/PyKotor/tests/tslpatcher/diff/test_diff_tslpatcher.py::TestTSLPatcherFromDiff::test_merge_tslpatcher_artifact_default_output_under_tslpatchdata Libraries/PyKotor/tests/tslpatcher/diff/test_diff_tslpatcher.py::TestTSLPatcherFromDiff::test_merge_tslpatcher_conflict_artifacts_json_matches_files Libraries/PyKotor/tests/tslpatcher/diff/test_diff_tslpatcher.py::TestTSLPatcherFromDiff::test_normalize_merge_conflict_policy_defaults_unknown_to_mod_a Libraries/PyKotor/tests/tslpatcher/diff/test_diff_tslpatcher.py::TestTSLPatcherFromDiff::test_serializer_uniquifies_triplicate_modifier_section_names -v — all passed.

• 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

AgentDecompile status: Skipped - tests only; no game-engine or binary behavior change :(