feat: Add ChanSink for sending stream items to a Go channel (attempt 2)

[vladimirvivien]

The ChanSink allows streaming data from an Automi pipeline to be collected into a channel. Items in the channel can be accessed as shown below:

src := sources.Slice([][]string{ ... }
snk := sinks.Chan[[]string]()
strm := From(src)
strm.WithLogSink(sinks.Func(testutil.LogSinkFunc(t)))
strm.Into(snk)

...
var receivedData [][]string
for data := range snk.Get() {
    receivedData = append(receivedData, data)
}

See documentation for detail.

Fixes #42

[Copilot]

Pull Request Overview

Adds a new ChanSink component for streaming pipeline items into a Go channel, complete with generics support, context cancellation, and tests.

• Introduces ChanSink[T any] and constructor Chan[T any](outputChan chan T).
• Implements streaming logic with type assertions, context handling, and channel closure.
• Adds unit tests covering normal flow, context cancellation, and wrong-data-type scenarios.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
sinks/chansink.go	Implements the generic ChanSink with Open, SetInput, Get, and logging.
sinks/chansink_test.go	Adds three test functions validating basic flow, context cancellation, and type errors.
go.mod	Removes the explicit toolchain directive.

Comments suppressed due to low confidence (2)

sinks/chansink_test.go:26

• [nitpick] The name sinkErr implies a single error value, but this is actually a channel of errors. Consider renaming to sinkErrCh to clarify its type.

sinkErr := cs.Open(ctx)

sinks/chansink_test.go:58

• Rather than inferring closure indirectly, add an explicit assertion to verify cs.Get() is closed, e.g.:

if _, ok := <-cs.Get(); ok {
    t.Error("expected output channel to be closed")
}

// Check if the sink's output channel was closed by the sink (indirectly via the receiving goroutine)