Support ElevenLabs Scribe v2

[pragmatrix]

Clarify:

• Do we need to convert language codes conversion (or is this a outside requirement). We want BCP47 at the boundaries, so yes

[Copilot]

Pull request overview

Adds an ElevenLabs Scribe v2 Realtime speech-to-text integration to the Context Switch service ecosystem, including a small core utility to convert language codes so BCP47 can be used at API boundaries.

Changes:

• Introduces a new services/elevenlabs crate implementing ElevenLabsTranscribe via a realtime WebSocket client.
• Adds core::language helpers (BCP47 ↔ ISO 639) and wires them into the ElevenLabs service.
• Registers the new service in the main registry and adds an example + documentation/env updates.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/lib.rs	Re-exports ElevenLabsTranscribe from the new service crate.
src/context_switch.rs	Registers elevenlabs-transcribe in the service registry.
services/elevenlabs/src/transcribe.rs	Implements ElevenLabs realtime transcription service logic and language conversion.
services/elevenlabs/src/lib.rs	Exposes the ElevenLabs transcribe module/type.
services/elevenlabs/Cargo.toml	Adds the new service crate manifest and dependencies.
README.md	Documents ElevenLabs integration and example usage/env var.
examples/elevenlabs-transcribe.rs	Adds a runnable example for ElevenLabs realtime transcription.
core/src/lib.rs	Exposes the new language module publicly from core.
core/src/language.rs	Implements BCP47/ISO639 conversion utilities with unit tests.
core/Cargo.toml	Adds dependencies needed for language-tag parsing/conversion.
Cargo.toml	Adds the new crate to workspace members and dependencies.
.github/copilot-instructions.md	Updates repository Copilot guidance.
.env.example	Adds ELEVENLABS_API_KEY template.