fix(gooddata): preserve grain for aliased primary-key fields

[mattfaltyn]

Summary

• Preserve GoodData dataset grain when an Ossie attribute uses a logical field name that differs from its physical primary-key column.
• Match primary_key entries against the converted attribute's source_column, which is already derived from the ANSI SQL expression.
• Cover both explicit dimensions and MAQL-detected attributes with regression cases.

This keeps the existing behavior for fields whose logical and physical names match while preventing silent loss of key/grain semantics for aliased fields.

Related Issues

Closes #346

Validation

Python 3.12: uv run --python 3.12 --frozen pytest -q  -> 76 passed
Python 3.13: uv run pytest -q                         -> 76 passed
Python 3.14: uv run --python 3.14 --frozen pytest -q  -> 76 passed
uv run ruff check src tests                           -> passed
git diff --check                                      -> passed

Checklist

Specification

• No specification changes

Converters

• Converter logic is updated
• Regression coverage is included under the GoodData test directory

Documentation

• Existing documentation was reviewed; no update is needed because this restores the documented primary-key-to-grain mapping without changing the interface

Tests

• All GoodData tests pass across the CI Python matrix
• New behavior is covered by tests

Compliance

• No new source files or dependencies