v5.6.0

chore(main): release 5.6.0 (#518)

Release PR for **5.6.0** — [compare
v5.5.0...v5.6.0](https://github.com/deepgram/deepgram-js-sdk/compare/v5.5.0...v5.6.0)

## What's in 5.6.0

- **[#515](https://github.com/deepgram/deepgram-js-sdk/pull/515) — Flux
TTS streaming (Speak V2) + agent listen reconfigure**
- **Speak V2 streaming (WebSocket)** — `client.speak.v2.connect(...)` →
`SpeakV2Socket`: new `speak/v2` package and `SpeakV2*` types, wired into
`DeepgramClient` with a binary-aware socket (mirrors the `speak.v1`
pair) so audio frames aren't JSON-parsed away.
- **Agent mid-session listen reconfigure** — `AgentV1UpdateListen` /
`AgentV1UpdateListenListen` messages with the `AgentV1ListenUpdated`
acknowledgement.
- **Flux end-of-turn tuning** — new `DeepgramListenProviderV2` fields
`eot_threshold`, `eager_eot_threshold`, `eot_timeout_ms`.
- **Reliability** — unknown/future server frames pass through untouched
(forward-compat); `ListenV2CloseStream` type corrected to only
`CloseStream`.

- **[#519](https://github.com/deepgram/deepgram-js-sdk/pull/519) — Flux
TTS batch (REST) + agent latency report**
- **Speak V2 batch (REST)** — `client.speak.v2.audio.generate(...)`: the
REST companion to streaming. New `SpeakV2Request` / `SpeakV2Response` /
`SpeakV2AcceptedResponse`, `AudioGenerateRequest*` types, and the
`./speak/v2/audio` export.
- `sample_rate` / `bit_rate` serialize as integers (no decimal) — a
float is rejected on the wire.
- Callback mode returns the ack as raw bytes (read via `arrayBuffer()`),
not a typed `SpeakV2AcceptedResponse`; parse `request_id` yourself.
  - **`AgentV1LatencyReport`** — new agent latency-report type.
- **Agent inject-message `interrupt`** — new value on the inject-message
behavior.

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