feat(client): add shape/flat/flat_lists to reference-data endpoints

[makegov-mark]

Summary

• The tango API has always supported the shape system on NaicsCodeViewSet, ProductServiceCodeViewSet, AssistanceListingViewSet, BusinessTypesViewSet, and MasSinsViewSet (all use ShapeOnDemandMixin), but the SDK didn't expose shape / flat / flat_lists on the corresponding methods.
• Adds the three pass-through params to ten methods: list_naics/get_naics, list_psc/get_psc, list_assistance_listings/get_assistance_listing, list_business_types/get_business_type, list_mas_sins/get_mas_sin.
• When shape is omitted the API applies its own per-resource default (e.g. code,description for NAICS list, name,code for business_types) — existing callers see no behavior change. list_business_types returns raw dicts when a shape is supplied, otherwise still yields BusinessType instances.
• Agencies/offices/departments deliberately left out of scope.

Why

NAICS was missing shape, and a sweep of the tango viewsets found four other reference-data resources in the same boat. The existing conformance script (scripts/check_filter_shape_conformance.py) only validates filter parameters, not shape support, so this drift was invisible. A follow-up can extend that script to assert SDK methods expose shape whenever the viewset uses ShapeOnDemandMixin / ShapedByDefaultMixin.

Test plan

• uv run ruff format . + uv run ruff check .
• uv run mypy tango/ — strict, clean
• uv run pytest tests/ -m "not integration" --ignore=tests/production — 300 passed
• uv run python scripts/check_filter_shape_conformance.py --manifest ../tango/contracts/filter_shape_contract.json — no errors
• Smoke against live API once merged (production-smoke saw an unrelated 504 locally)

Risks

• Public-surface addition only (new optional kwargs with None / False defaults) — non-breaking.
• list_business_types return type widens to BusinessType | dict when callers opt into shape; the annotation was already unparametrized PaginatedResponse, so existing typed callers are unaffected.

Next steps

• Optional follow-up: teach the conformance script to verify shape-param exposure so this class of drift can't recur.

~ Mark