…ed-ChatClientAgent to source (ZIP)

Foundry.Hosting: AddFoundryResponses now binds Kestrel to FoundryEnvironment.Port (the PORT env var, default 8088) for a plain WebApplication.CreateBuilder (Tier 3) host, mirroring AgentHostBuilder. This lets a source/ZIP-deployed .NET agent pass the readiness probe with no Dockerfile. It respects an explicit ASPNETCORE_URLS override and is idempotent. Adds FoundryListenPortTests plus a serialized env-var collection.

Hosted-ChatClientAgent: migrate to source (ZIP) deploy as the default. Add azure.yaml with codeConfiguration (remote_build, dotnet_10) and the tool-generated .agentignore, make the csproj self-contained (single target, CPM off) with a local Directory.Packages.props, embed the local-dev per-agent route so the Using-Samples REPL can reach the local server, and rewrite the README around the azd flow. Documents AZURE_TOKEN_CREDENTIALS=dev for local runs.

Using-Samples/SimpleAgent: fix the per-agent endpoint scheme rewrite so the local HTTP dev port is preserved (the policy now lives on the per-agent ProjectOpenAIClientOptions that actually serves the request).

…and the local-only agent route

Zip/code deploy runs the sample as a plain ASP.NET app, so the Foundry readiness
port was never bound and every invoke returned HTTP 424 session_not_ready. The
first attempt skipped the binding when ASPNETCORE_URLS was already set, but the
.NET base image always sets it to port 80, so the skip always tripped. Kestrel
ListenAnyIP overrides ASPNETCORE_URLS, so the binding is now unconditional and
PORT stays the only knob.

Sample cleanup for zip deploy:
* Remove Dockerfile, Dockerfile.contributor, agent.manifest.yaml and agent.yaml.
  Source deploy needs none of them.
* Remove LocalDevEndpoint.cs and the invented per-agent local route. The local
  server already serves the standard POST /responses route, so the client can
  reach it directly.
* Trim .env.example: the port and environment variables are no longer needed.
* Exclude .checkpoints/ from the upload so local session state does not ship.

SimpleAgent now asks at startup whether to chat with the local server or the
deployed agent, the same choice azd ai agent invoke exposes through --local.
Local uses an OpenAI responses client pointed at http://localhost:8088; Foundry
uses the per-agent endpoint.

Add scripts/New-ContributorStage.ps1, which stages a sample to a temp folder with
the local Agent Framework source packed into a feed inside the upload, so
contributors can deploy framework changes through the same azd flow end users run.

…tion