refactor(session): collapse the request openers into a generic helper

[floatdrop]

What

Publish, Subscribe, Fetch, TrackStatus, PublishNamespace, SubscribeNamespace, and SubscribeTracks all repeated the same §10.1 request skeleton:

openAllocRequest(m) → readResponse(ctx) → switch { OK / REQUEST_ERROR / default } → wrap

Fetch and TrackStatus even carried //nolint:dupl waivers acknowledging the duplication.

This extracts a single generic primitive, awaitRequestResponse[OK, R], in request.go. It owns the open / await-OK / error-mapping skeleton and delegates only the success case — the expected OK message type and the typed-handle construction — to a per-opener closure:

func (s *Session) Subscribe(ctx context.Context, m *message.Subscribe) (*Subscription, error) {
	return awaitRequestResponse(ctx, s, m,
		func(stream Stream, ok *message.SubscribeOK) (*Subscription, error) {
			// validate properties, register alias, wrap…
		})
}

The REQUEST_ERROR → *RequestRejectedError mapping, the unexpected %s in X response error, and the read X response wrapping now live in one place instead of seven. The operation name in those errors is derived from m.Type() (which already stringifies to SUBSCRIBE, FETCH, TRACK_STATUS, …), so there is no redundant label to keep in sync.

Publish keeps its one distinguishing step — pre-allocating the Track Alias before the open — in the method body, then routes through the same helper (OpenPublish is just openAllocRequest, which the helper already calls).

Why

• Removes ~170 lines of near-identical boilerplate.
• Deletes both //nolint:dupl waivers — the duplication is gone, not suppressed.
• Centralizes the response-dispatch and error-mapping logic so future changes (e.g. the "self-close on protocol violation" cleanup) touch one function.

Behavior

No behavior change. The helper checks the OK type first, then REQUEST_ERROR, then falls through to the unexpected-response error — identical ordering, outcomes, and error strings to the original type switches. OK is matched via a type assertion on the type parameter, which keys on the concrete wire type (*SubscribeOK, *FetchOK, *RequestOK; note TrackStatusOK = RequestOK).

Testing

• go build ./...
• go test ./... (full suite)
• go test -race ./pkg/moqt/session/... ./pkg/relay/...
• golangci-lint run ./pkg/moqt/session/... — 0 issues

🤖 Generated with Claude Code