fix(examples): use d_moy for the TPC-DS date_dim month field

[kayemkim]

Summary

examples/tpcds_semantic_model.yaml declares a d_month_name field on date_dim with expression: d_month_name. TPC-DS has no such column. The month column is d_moy (1-12); d_day_name and d_quarter_name do exist, which is probably where the name came from. A conversion round-trip never touches the physical table, so the field converts cleanly in every suite and only fails when something executes the model against real TPC-DS data, as reported in #358.

This renames the field and its expression to d_moy and updates the description. Several converter fixtures are copies or conversions of the canonical example, so the same rename is applied to them, both to keep them consistent and because the omni tests export the canonical example and compare it against the tpcds_omni fixture:

• converters/orionbelt/tests/fixtures/: tpcds_ossie.yaml, tpcds_semantic_model.yaml, tpcds_as_obml.yaml
• converters/omni/tests/fixtures/tpcds_omni/views/date_dim.view.yaml
• converters/snowflake/tests/example_converted_tpcds_semantic_model.yaml

The field keeps is_time: true with no datatype, since the comment above it uses this field to show that the two annotations are independent.

Separately, two orionbelt fixtures (tpcds_ossie.yaml, obml_as_ossie.yaml) still declared version: 0.1.1, which the schema's version const rejects. They now declare 0.2.0.dev0. No test loads either file, so this only changes standalone validation. Whether version should remain a const is a separate question raised in #357; this PR only brings the fixtures in line with the schema as it stands.

Checked:

• DuckDB tpcds extension at sf=0.01: date_dim has 28 columns, none named d_month_name; d_moy resolves.
• validation/validate.py passes on the canonical example and on all three orionbelt Ossie-format fixtures. Before this change tpcds_ossie.yaml failed with '0.2.0.dev0' was expected.
• Converter tests: orionbelt 154 passed, omni 83 passed / 3 skipped, snowflake 107 passed, honeydew TPC-DS round-trip passed.
• grep -rn d_month_name over the repo returns nothing.

Related Issues

Fixes #357. Fixes #358.

Checklist

Specification

• Spec changes are included in core-spec/ and follow the existing structure
• Spec changes have been discussed on the mailing list or in a linked issue
• Breaking changes to the spec are clearly called out in the summary

Ontology

• Ontology changes in ontology/ are consistent with spec changes
• New or modified terms are defined and documented

Converters

• Converter logic in converters/ is updated to reflect spec or ontology changes
• New converters include tests under the converter's test directory

Validation

• Validation rules in validation/ are updated if the spec changed
• New validation cases are covered by tests

Documentation

• docs/ is updated to reflect any user-facing changes
• New features or behaviors are documented with examples where appropriate
• CONTRIBUTING.md is updated if the contribution process changed

Examples

• examples/ are added or updated for any new spec constructs or converter support

Tests

• All existing tests pass (pytest / CI green)
• New functionality is covered by tests

Compliance

• ASF license headers are present on all new source files
• No third-party dependencies are added without PMC/IPMC approval