Cleanup from self-review: redundant abspath, missing DeprecationWarning, logger inconsistency, eager __eq__

[iskandr]

Small fixes surfaced while re-reading the past week's work with a critical eye. No behavior changes visible to normal callers; one API nicety (`DeprecationWarning`).

Changes

`mhctools/mhcflurry.py`

• `_normalize_models_path`: drop redundant `os.path.abspath()`. `os.path.realpath()` already returns an absolute path.
• Replace two stray `logging.info(...)` calls with `logger.info(...)`, using the module logger defined at line 25 (pre-existing inconsistency, fixed while nearby).

`mhctools/base_predictor.py`

• `predict_peptides_dataframe` has said "Deprecated" in its docstring for a while; now emits `DeprecationWarning` with `stacklevel=2` so callers get a runtime signal to migrate to `predict_dataframe()`.

`mhctools/cli/args.py`

• `_LazyPredictor.eq`: short-circuit on `is` identity and on non-class operands. Previously, `BigMHC == some_random_object` would eagerly `_resolve()` (importing torch) just to return `False`. Now it returns `NotImplemented` without triggering the import.

`tests/test_dataframe_schema_parity.py`

• New test asserting `DeprecationWarning` fires.
• Existing schema tests silence the warning locally so it doesn't pollute unrelated assertions.

Test plan

• `pytest tests/` (non-integration subset) — 83 passed
• `DeprecationWarning` fires and is caught via `pytest.warns`
• Existing `_LazyPredictor` comparisons in `test_cli_registry` still pass (they compare against real class objects, which hit the `isinstance(other, type)` branch and resolve as before)

No version bump needed — these are internal refinements. Will batch with the next substantive change.