* .NET: Hosted Agents - RAG Sample with Azure AI Search (#5693)
Adds a Hosted-AzureSearchRag sample plus a live Foundry.Hosting integration
test scenario backed by a real Azure AI Search index.
Sample (Hosted-AzureSearchRag): keyword-only Azure AI Search via
SearchClient adapter into TextSearchProvider, scope-aware
DevTemporaryTokenCredential consuming AZURE_BEARER_TOKEN_FOUNDRY +
AZURE_BEARER_TOKEN_SEARCH for local Docker, Dockerfile + contributor
Dockerfile mirroring Hosted-TextRag.
Integration test: AzureSearchRagHostedAgentFixture extends the PR #5598
HostedAgentFixture with the new azure-search-rag scenario branch in the
shared test container; AzureSearchRagHostedAgentTests asserts the model
returns canary tokens (TR-CANARY-7821, SHIP-CANARY-4493) that exist only
in the seeded documents - real proof the agent grounded its answer in
retrieved content rather than training data.
* Address PR 5701 Copilot review feedback
- Sample README: drop stale 'bootstraps the index on first run' line; index is pre-provisioned out of band
- Sample + TestContainer search adapters: propagate CancellationToken to await foreach via .WithCancellation()
Roger Barreto