feat: add Camb.ai TTS extension

[eRuaro]

Summary

• Add camb_tts extension for text-to-speech using Camb.ai's MARS API
• Follows the established HTTP-based TTS pattern
• Includes unit tests with mock client

Features

• MARS model family support (mars-flash, mars-pro, mars-instruct)
• 140+ languages supported
• Real-time HTTP streaming
• Configurable voice, language, and model

Configuration

{
  "params": {
    "api_key": "${env:CAMB_API_KEY|}",
    "voice_id": 147320,
    "language": "en-us",
    "speech_model": "mars-flash",
    "format": "pcm_s16le"
  }
}

Test plan

• Manual API test with real Camb.ai API key
• Audio playback verified
• Unit tests with TEN Framework test harness

[plutoless]

hi @eRuaro thanks for your pr! please run the formatter and lint and fix relevant issues so that we can merge your pr after ci passes. thx!

[eRuaro]

will do! thanks!

[eRuaro]

@plutoless sorry for the delay! this recent commit fixes the formatting errors you mentioned.

[eRuaro]

@plutoless hey ethan! following up on this - would love to see camb ai on ten!