Remove unapproved compatibility interfaces for 0.2 #65

Affected version

ml4t-data 0.1.8 and the 0.1 release line.

Compatibility assessment

The ecosystem inventory permits only QLDM_DATA_ROOT and QldmError as retained deprecated identifiers in Data. The 0.1 line also preserves PolygonProvider, the polygon registry name, check_negative_prices, and garch_omega with runtime warnings. Retaining them would violate the stable-library qualification contract. Removal is intentionally incompatible and therefore targets 0.2, not a 0.1 patch release.

The unused root api.yaml also claims version 1.0.0 and records stale quotas and unsupported comparisons. No source, test, workflow, or documentation code reads it; current package metadata and generated API documentation are authoritative.

Acceptance criteria

• Remove the three unapproved compatibility interfaces and the unused deprecated real_api marker.
• Remove the stale root API manifest and Polygon compatibility page.
• Keep MASSIVE_API_KEY canonical while continuing to accept existing POLYGON_API_KEY credentials.
• Document the 0.2 migration for imports, registry configuration, validation settings, and synthetic GARCH settings.
• Add runtime contract tests that prove the removed APIs are absent or rejected.
• Pass focused tests, the full repository quality suite, strict documentation, package build, and ecosystem qualification.

User impact and migration

Existing callers must migrate before 0.2. The migration guide will provide exact replacements. No 0.1.x release should contain this removal.