refactor(reasoning)!: remove Node-RED engine and integrations

BREAKING CHANGE: NODE_RED reasoning is no longer supported. Unsupported
mode values fall back to PROXY. PROXY and OPENAI remain available.

s2s-frontend/README.md

@@ -115,7 +115,7 @@ by Git. The launcher serves source through Vite; it does not use `dist/` or
 
 Tests cover session initialization, response sequencing, cumulative transcripts,
 interruptions, queue polling, admission deadlines, cancellation, microphone-permission cancellation, tool
-results, external reasoning and `LOG_ONLY`, late-response cleanup, the idle
+results, external reasoning, late-response cleanup, the idle
 timeout, settings, RAG, profiles, and sanitized Markdown/export behavior.
 Launcher tests start temporary local children to check readiness, environment
 forwarding, failures, and shutdown of complete process groups.
@@ -144,8 +144,7 @@ quick actions remain absent, matching their disabled state in the old UI.
 Native speech stays at the current project's 16 kHz PCM rate. The backend
 continues to own VAD, transcription, model inference, synthesis, upstream
 credentials, and ApiPilot execution. Browser `SpeechSynthesis` is used only
-when the configured external reasoning service returns an answer instead of
-`log_only`.
+when the configured external reasoning service returns an answer.
 
 Session startup waits for audio initialization and `session.created`, then sends
 `session.update` before microphone audio or the initial greeting. The speech