docs: identify released migration inputs and consumer boundaries #137

Package/documentation version: ml4t-data 0.3.0, published source db9cda7.

Location: https://www.ml4trading.io/docs/data/getting-started/migration/

Problem: the live guide has six statements that the migration APIs/workflows are unreleased, although the published 0.3.0 wheel contains and passes the maintained migration examples. It also says Engineer 0.1.7 is unpublished and recommends an old development checkout; Engineer 0.2.0 is now on PyPI. The guide mixes historical source integration qualification with current Data installation instructions.

Required outcome: identify released Data 0.3.0 inputs/adapters, link runnable examples at its immutable source, and explain the Diagnostic and Backtest consumption boundaries. Retain historical integration evidence with its actual source/version limits, rather than promoting it to an untested current consumer stack. Preserve all data, adjustment and runtime limitations.

Acceptance: verify the live page identity and installed public 0.3.0 APIs/examples; correct release availability and stale installation advice; strict MkDocs and rendered internal/example-link checks pass. No runtime changes or claim of complete Reloaded replacement. Keep the already qualified 0.3.1 source cut unchanged and hold merge behind the release-source decision.

AI assistance: Codex reproduced the documentation mismatch and prepares the documentation correction and verification evidence under maintainer direction.