feat: namespaced SDK (client.agent / client.tts) + realtime connect layer

[luke-speechify]

What

Regenerates the SDK from the updated OpenAPI spec and adds a hand-written realtime voice-agent connect layer.

1. Namespaced surface (spec-driven)

Operations are now grouped so the client reads as the product does:

• client.tts.audio.*, client.tts.voices.*
• client.agent.* — core agent CRUD flattened onto agent (create, get, list, update, delete, createConversation, …)
• client.agent.{conversations, tools, knowledgeBases, tests, phoneNumbers, …} — 14 sub-resources

Spec-only change (x-fern-sdk-group-name); no wire/field renames.

2. @livekit/rtc-node dependency

Added via generators.yml extraDependencies so the realtime transport ships with the package.

3. Realtime connect layer — @speechify/api/realtime

Hand-written, .fernignore'd (src/realtime/). Exposes a realtime voice-agent session from the { url, token } returned by client.agent.createConversation(...):

import { connectConversation } from "@speechify/api/realtime";

const convo = await client.agent.createConversation(agentId, { /* ... */ });
const session = await connectConversation(convo);

session.onText((ev) => console.log(ev.role, ev.text, ev.final));
for await (const chunk of session.outputAudio()) { /* PCM16 LE */ }
await session.sendAudio(callerPcm, { sampleRate: 48000, channels: 1 });
await session.disconnect();

• Audio is exposed as raw PCM byte streams (input + output) — no microphone/speaker capture; device handling is the application's job.
• Transcripts via onText ({ role, text, final }).
• The realtime transport is an internal implementation detail and never named in the public surface.

Verification

• fern generate --group typescript --local → builds clean (tsc, 0 errors)
• Structure smoke: tts.audio/voices present, tts has no agents, flat agent.* + 14/14 sub-resources
• Realtime layer proven end-to-end against a live agent (caller WAV in → agent reply audio + transcripts out)
• @speechify/api/realtime subpath resolves to the compiled module after prepack

Draft until the sibling api-repo generators.yml PR lands.