feat!: add endpoint conventions and metadata for 2.0.0-preview.2

[ling921]

What changed

• Add typed convention builders at registry, service, and individual operation scopes for endpoint filters and common ASP.NET Core endpoint conventions.
• Add contract attributes for endpoint metadata, with optional HTTP method selectors, and emit the corresponding native Minimal API metadata from the source generator.
• Inherit method declarations, metadata, policies, parameter binding, and XML documentation through service interface hierarchies; report conflicting inherited declarations and duplicate endpoint names at compile time.
• Update the English and Chinese documentation and changelog for the corrected 2.0.0-preview.2 package version.

Breaking changes

This is the first usable 2.0.0 preview. RemoteMethodAttribute.SuccessStatusCode is now a non-nullable int because nullable types are not valid CLR attribute named-argument types; 0 retains the default success status behavior.

The earlier v2.0.0-preview.1 GitHub tag was accidentally created from master and has been marked withdrawn. Its workflow found only existing 1.0.0 packages and published no 2.0.0 packages.

Validation

• Windows Release tests passed for the supported target frameworks.
• Linux Release packaging passed, including Native AOT client/server roundtrip and all three NuGet packages.
• Windows package build verified all three package manifests are versioned 2.0.0-preview.2.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Reject invalid policy HTTP-method selectors

When a policy attribute uses an out-of-range selector, such as [RemoteAuthorize("Admin", HttpMethod = (RemoteHttpMethod)99)], this branch silently skips it for every operation without reporting a contract diagnostic. In the authorization case that can leave the endpoint unprotected despite an explicit authorization declaration; validate the selector before filtering, as EndpointMetadataParser already does for non-policy metadata.

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[chatgpt-codex-connector]

Restrict successful endpoint statuses to 2xx

This validation accepts informational statuses from 100 through 199 as SuccessStatusCode. An attribute such as [Get(SuccessStatusCode = 100)] therefore generates an endpoint that attempts to use an informational response as its final result, while the generated client checks HttpResponseMessage.IsSuccessStatusCode and treats every non-2xx response as a failure. Reject values below 200 so server and client agree on what constitutes success.

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