feat(models): update Python SDK schemas for UCP release 2026-08-25

[segiodongo]

Description

This PR updates the Python SDK to be fully compatible with the UCP 2026-08-25 specification release.

Key Changes

1. Schema Preprocessing & Codegen Pipeline:

   • Added list/dict type-safety guards to preprocess_schemas.py for allOf, anyOf, and oneOf merging.
   • Updated normalize_metadata_schemas to dynamically detect and include all UCP metadata response envelopes (including response_catalog_schema and response_location_schema).
   • Extended per-file-ignores in pyproject.toml for generated schemas, preprocessing/postprocessing scripts, and test suites.

2. Model Regeneration & Reorganization:

   • Regenerated all Pydantic v2 models using ./generate_models.sh 2026-08-25.
   • Common Vertical (ucp_sdk.models.schemas.common): Added models for Location Search & Lookup (location_search.py, location_lookup.py), Loyalty, Payment Terms, AP2 Mandates, Split Payments, and Request Constraints.
   • Shared Primitives (ucp_sdk.models.schemas.common.types): Relocated shared types (amounts, prices, totals, postal address, signals, error/warning messages, pagination, time interval, unit price) from shopping into the common namespace.
   • Shopping Vertical (ucp_sdk.models.schemas.shopping): Updated Cart, Checkout, Order, Catalog Search/Lookup, Buyer Consent, and Permalinks to reference the reorganized common types and new fulfillment destinations.
   • Transports (ucp_sdk.models.schemas.transports): Generated transport bindings for REST, MCP tool calls, JSON-RPC, and embedded/A2A messaging.
   • Service & Profile (ucp_sdk.models.schemas): Added profile.py and updated capability/service definitions.

3. Documentation & Versioning:

   • Bumped package version to 0.5.0 in pyproject.toml and src/ucp_sdk/__init__.py.
   • Updated README.md package reference table and codegen instructions.
   • Configured .gitignore to ignore temporary codegen artifacts (ucp/, uv.lock).

Verification

• Linting & Formatting: uv run ruff format and uv run ruff check passed cleanly (0 errors).
• Unit Tests: uv run python -m unittest discover tests/ passed (88 tests passed, 0 failures).
• Module Import Health: Dynamically imported all 226 generated model submodules with 0 import errors.

[carolinerg1]

Hi @segiodongo,

Thanks for submitting this PR! Looks like it's failing backward compatibility when regenerating models for 2026-04-08 and Lint - though I see in your description that you ran Lint check (potentially not across all updated files ?). Could you please take a look at these 2 issues. Thanks!