[tracyboehrer (tracyboehrer)]

Summary

• Update all 65 direct Agents SDK package references across 26 .NET sample projects to 1.9.*, including the production reference's previously pinned packages.
• Align the Teams contract-test SDK version with 1.9.* and update the production reference's version guidance.
• Synchronize all 23 AspNetExtensions.cs copies byte-for-byte with the upstream shared helper.
• Leave separate Agent Framework package versions unchanged.

Generated Teams agent implementations and contract-test source files are unchanged. Copilot's temporary manual compatibility edits and additional meeting compatibility dependency were reverted at the maintainer's request.

Known blocker

Related issue: #783.

The generated Teams samples still use the older Microsoft.Teams.Api.* APIs, including Microsoft.Teams.Api.Meetings. Agents SDK 1.9 resolves Teams SDK 2.1's Microsoft.Teams.Apps / Microsoft.Teams.Core APIs instead.

The compatibility changes belong in the automated Teams synchronization process, not in manual edits to generated samples. This PR is a draft because the full solution build remains blocked by those obsolete Teams imports/types.

Validation

• Passed: all sample SDK references use 1.9.*; non-SDK package references and other project settings are unchanged.
• Passed: all 23 helper copies exactly match the upstream source; the staged helper blobs match the upstream Git blob.
• Passed: no generated Teams agent or contract-test implementation changes remain; git diff --check is clean.
• Retrieval sample tests: 10 passed.
• Production reference: 35 passed, 2 skipped. The optional Azurite integration tests were skipped; a temporary non-secret development configuration was supplied in the test output directory and removed afterward.
• Full dotnet build from samples\dotnet: fails with 20 compiler errors in the generated Teams samples, tracked in Regenerate .NET Teams samples for Agents SDK 1.9 and Teams SDK 2.1 #783.