[Channel RFC] Core abstractions package (Aevatar.GAgents.Channel.Abstractions)

[eanzhao]

Parent RFC: #254

Scope

Aevatar.GAgents.Channel.Abstractions package —— 核心接口层。

Deliverables

Interfaces (Aevatar.GAgents.Channel.Abstractions/):

• IChannelTransport (Runtime side: lifecycle + inbound stream + capabilities)
• IChannelOutboundPort (Dispatch side: send/update/delete/continue)
• IMessageComposer<TNativePayload> + IMessageComposer 通用
• IBot + ITurnContext (业务 bot logic 接口)
• IChannelMiddleware (窄范围横切：logging / tracing / conversation resolver)
• ICredentialProvider (see [Channel RFC] Phase 0 infra prerequisites (DeleteAsync / EventHubs harness / secret manager) #255)
• IPayloadRedactor (含 HealthCheckAsync)
• PerEntryDocumentProjector<TEntry, TDocument> 抽象基类（base 类抽取见 [Channel RFC] Base class extraction (PerEntryDocumentProjector + ISchedulable) #259）
• ISchedulable marker interface（见 [Channel RFC] Base class extraction (PerEntryDocumentProjector + ISchedulable) #259）

Hard constraint: single-class two-interfaces

• 禁止 "独立两个类实现"——IChannelTransport 和 IChannelOutboundPort 必须 single class 同时实现（init/auth/capabilities 共享 state）
• CI guard: channel_mega_interface_guard.sh 禁止 mega-interface 回归
• Conformance Suite 泛型约束 where TAdapter : IChannelTransport, IChannelOutboundPort

Types (from proto-generated in #256):

• C# record partial classes 在 proto-generated types 上扩展必要的 helper 方法（deterministic canonical key builders etc.）

Interface documentation:

• §5.8 Interface Contracts 全部内联为 XML doc comments（lifecycle / idempotency / ordering）

Acceptance

• Aevatar.GAgents.Channel.Abstractions.csproj 独立 build 通过
• 接口 surface 过 Abigail / Shining / Potter / Louis 架构 review（对齐 Commitment 2 盲区覆盖）
• XML doc 完整，CI 强制 no public API without doc

References

• RFC §5 核心接口设计（§5.1-§5.8 全章节）
• RFC §5.8 Interface Contracts

Dependencies

• Depends on: [Channel RFC] Proto schema definitions (7 proto files) #256