Select UK local-authority lookup by dataset identity

[anth-volk]

Add typed bundle metadata for LAD22 and LAD23 lookup assets. Resolve explicitly mapped legacy datasets to LAD22, default every other dataset to LAD23, verify managed asset hashes, and expose dataset-aware local-authority output selection.

[anth-volk]

Closed in favor of PolicyEngine/policyengine-sim-api#705. The Stage 12 executor now performs typed, code-based roster detection locally; PolicyEngine.py does not need dataset-identity routing for this temporary stage.

[anth-volk]

Update: the replacement simulation API work is now PolicyEngine/policyengine-sim-api#706. GitHub closed #705 when its branch was renamed.