docs: consolidate English documentation under root docs

docs/README.md

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+# Documentation
+
+All maintained documentation is in English. Spanish examples represent actual
+user input or spoken output. Historical proposals are identified explicitly and
+do not define the current implementation.
+
+## Browser client
+
+- [Usage and configuration](client/usage.md)
+- [Architecture and source map](client/architecture.md)
+- [Reasoning modes](client/reasoning.md)
+- [Context injection](client/context-injection.md)
+- [Tool calling](client/tool-calling.md)
+- [Design language](client/design.md)
+- [Glossary](client/glossary.md)
+- [Troubleshooting](client/troubleshooting.md)
+- [Change history](../s2s-client/CHANGELOG.md)
+
+## Speech backend
+
+- [Language model backends](speech/llm.md)
+- [Speech-to-text backends](speech/stt.md)
+- [Text-to-speech backends](speech/tts.md)
+- [Realtime API, tools, and interruption handling](speech/realtime-api.md)
+
+## Decisions, proposals, and examples
+
+- [Example files and usage](examples/README.md)
+- [ADR 0001: Docker hosting and search proxy](adr/0001-docker-space-with-search-proxy.md)
+- [Historical Vocero architecture proposal](proposals/vocero-architecture.html)
+- [Agent-profile example](examples/agent-profile.json): an illustrative profile
+  with agent instructions and tool definitions; this is not the current
+  `/api/config` response or an automatically loaded runtime configuration.
+- [Reference audio](examples/reference-audio.wav): an optional voice-cloning
+  example described in the [TTS guide](speech/tts.md).