[Search 2026-08-01-preview] python SDK codegen

[Copilot]

Regenerate azure-search-documents for Azure Search API 2026-08-01-preview from spec commit c19e358860e3cb89a8c7021e8c5a181ab6ef7f62.

Blocker: generator emits non-importable code (spec defect)

Running the documented generator (tsp-client update, emitter @azure-tools/typespec-python@0.63.3) against this commit yields a package that fails to import:

• The new 2026-08-01-preview request/response bodies are emitter-synthesized models (EntraAppAuthentication, FileUploadMetadata, KnowledgeBaseRetrieveDefaults, UploadKnowledgeSourceFileMultipartRequest, …) that resolve to the root Search TypeSpec namespace.
• That namespace has no blanket @@clientNamespace("Azure.Search.Documents") in client.tsp, so the emitter writes them to a top-level search/ package (sibling of azure/) and references them via from ......search import models → ImportError: attempted relative import beyond top-level package. The namespace=azure.search.documents emitter option makes it worse (azure.azure double-prefix).

The fix lives in the spec's client.tsp (Azure/azure-rest-api-specs), outside the allowed path sdk/search/azure-search-documents/**. Per "report blockers instead of hand-editing generated code to mask spec issues," the broken generated surface is not committed.

Changes (importable subset)

• _patch.py — add ApiVersion.V2026_08_01_PREVIEW, making the new version selectable on every client via the api_version keyword.
• Default unchanged — the effective client default comes from generated _configuration.py (a generated file, not hand-edited); bumping only the _patch.py DEFAULT_VERSION would desync SearchClient/SearchIndexingBufferedSender from the index/indexer/knowledgebase clients, so it's left at V2026_05_01_PREVIEW.
• tsp-location.yaml / _metadata.json — retarget spec commit c19e358 / 2026-08-01-preview.
• Tests — assert the enum member exists and flows to client config.
• CHANGELOG — new selectable version under Features Added; blocker documented under Other Changes.

from azure.search.documents import SearchClient, ApiVersion

client = SearchClient(endpoint, index_name, credential,
                      api_version=ApiVersion.V2026_08_01_PREVIEW)

Not included (needs spec fix first)

• Full model/operation regeneration from c19e358 (blocked by the client.tsp @@clientNamespace defect).
• Samples/tests for new 2026-08-01-preview features (SSE streaming retrieval, auto reasoning tier, multipart upload, WorkIQ auth, listing pagination).

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