feat(cli): deprecate console and dev modes in favor of lk agent

[u9g]

Console and dev modes are being removed from the Python framework. This adds the deprecation notices first, pointing users at lk agent console / lk agent dev and the CLI setup docs.

Surfaces, all in the legacy rich CLI:

• Console startup notice, using the existing tagged-print pattern (same mechanism as the Recording notice), so it shows in both audio and text mode:

    Agents   Starting console mode 🚀
 Deprecated  console mode is deprecated and will be removed in a future release.
             Use lk agent console instead: https://docs.livekit.io/reference/developer-tools/livekit-cli/#setup

• dev logs a deprecation warning at startup (alongside the existing auto-reload warning).
• console --help and dev --help both read Deprecated: use lk agent <cmd> instead.

run_app already emits a generic DeprecationWarning for the whole legacy Python CLI, so no second command-specific warnings.warn here — this fills the gap in per-command migration guidance.

The TCP console in cli.py is untouched; that is the path lk agent console drives, not the one being deprecated.

[devin-ai-integration]

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