feat(adapters): align channel adapter with RFC 1

[Garfield550]

Summary

• align the channel adapter send path and terminal handling with RFC 1 semantics
• preserve original channel writer failures, fail fast on transient outbound pressure, and keep transport-fatal ordering deterministic for pending unary and active stream invokes
• respect CompleteOutboundOnDispose for custom endpoints on remote close and fault, and document the intentional malformed-input regression probe in tests

Validation

• dotnet test --project tests/Eventa.Adapters.Tests/Eventa.Adapters.Tests.csproj --configuration Release --filter-class Eventa.Adapters.Tests.Channels.ChannelPipeTests
• dotnet test --project tests/Eventa.Tests/Eventa.Tests.csproj --configuration Release
• dotnet build Eventa.slnx --configuration Release --no-restore

[Copilot]

Pull request overview

This PR aligns the Eventa.Adapters.Channels transport behavior with RFC 1, focusing on deterministic terminal handling and clearer outbound-send semantics under terminal states vs. transient outbound pressure.

Changes:

• Update channel adapter send path to fail fast on transient outbound pressure while preserving original channel-writer failure exceptions when terminal.
• Adjust endpoint termination to respect CompleteOutboundOnDispose for remote close/fault and harden cancellation races during termination.
• Expand/refresh channel adapter tests to cover deterministic ordering (invoke/stream faults vs. closed event), writer-failure propagation, and disposal races; update docs to reflect adapter/AOT posture.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/Eventa.Adapters.Tests/Channels/ChannelPipeTests.cs	Adds/updates tests for RFC-1 terminal ordering, fail-fast behavior, and exception-shape preservation.
src/Eventa/Support/AsyncSignalQueue.cs	Switches channel options to allow synchronous continuations (behavioral change).
src/Eventa.Adapters/Channels/ChannelMessages.cs	Makes ChannelMessage.Envelope non-nullable (tightens contract).
src/Eventa.Adapters/Channels/ChannelEndpoint.cs	Uses CompleteOutboundOnDispose for inbound close/fault termination and hardens CTS cancellation against disposal races.
src/Eventa.Adapters/Channels/ChannelAdapter.cs	Implements non-blocking send probing to distinguish transient backpressure from terminal writer state; preserves writer exception shapes.
README.md	Documents adapter/AOT characteristics and clarifies channel adapter constraints.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.