chore: initialize from backend template 0a6dd0e

docs/httpclient/streaming.md

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+# Streaming and Large Bodies
+
+## Response lifecycle
+
+A blocking streaming download returns `BlockingStreamingResponse`, never a bare `InputStream`.
+Closing is idempotent and always releases the connection — after a full read, a partial read, a
+decode failure, or a size rejection. The status is validated before any body byte is delivered, so a
+failed download never becomes a half-consumed stream the caller has to reason about.
+
+A reactive download emits bounded `DataBuffer` values. Buffers are released on completion, error,
+and cancellation; a dropped buffer is direct memory nobody returns.
+
+Wire bytes and decoded bytes are bounded independently, because a compressed payload passes a wire
+check and then expands. Limits are enforced while reading, not after buffering.
+
+## The first-byte boundary
+
+```text
+response headers received
+  → nothing delivered yet
+     → a read-only operation may still be retried
+  → first InputStream read or first Flux onNext
+     → transparent retry is permanently disabled
+```
+
+`FirstByteDeliveryGuard` latches once and never resets. Retrying after delivery would replay a
+stream the caller has already partly consumed, producing duplicated or reordered data that no
+downstream code can detect.
+
+## Request bodies
+
+A reopenable body is opened once per attempt, which is what makes it replayable; reusing the
+previous stream would silently send an empty body on the retry. A one-shot stream or publisher
+instance is never retried. `ReactiveBodySource` takes a publisher *factory* rather than a publisher
+so a reactive body can honestly declare itself replayable.
+
+A multipart body is exactly as replayable as its weakest part.
+
+## Server-sent events
+
+Three budgets stay separate:
+
+- `setupDeadline` — establishing the stream
+- `streamingIdleTimeout` — silence once it is open
+- `maxStreamDuration` — optional total lifetime
+
+Applying the request-shaped `total-call` timeout to an SSE subscription would terminate a perfectly
+healthy stream on schedule, so it is not applied.
+
+`Last-Event-ID` is opt-in. Replaying from an id is only correct when the producer guarantees it;
+sending it blindly can skip or duplicate events. Reconnects consume the retry budget like any other
+physical attempt, and cancelling the subscription stops both the stream and any pending reconnect.