feat: bootstrap vela UI and gateway workspace

Establish the monorepo, tooling, and starter apps so UI and gateway development can begin from a documented, runnable baseline.

docs/overview.md

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+# Vela Overview
+
+## Objective
+
+Vela is a fully local, voice-first assistant system with:
+
+- local-first architecture and no mandatory cloud dependencies
+- natural TTS output via Kokoro
+- voice-driven interaction as the primary interface
+- integrations with Home Assistant and SearXNG
+- a lightweight SvelteKit PWA
+- remote LLM inference via Ollama on a NAS
+
+## Core Design Principles
+
+### Voice-first
+
+- UI optimized for speaking instead of typing
+- minimal visual clutter
+- real-time feedback through partial transcripts and streaming responses
+
+### Local-first
+
+- no required cloud APIs
+- all services self-hosted
+- browser used for capture and playback only
+
+### Tool-driven intelligence
+
+- the LLM does not directly control external systems
+- all external actions route through explicit tools
+
+### Low-latency interaction
+
+- streaming STT partial results
+- streaming LLM token output
+- streaming TTS audio chunks
+- interruptible responses
+
+## Product Scope
+
+### Primary Interface
+
+- browser-based PWA
+- push-to-talk interaction
+- transcript and response display
+- playback of streamed or returned audio
+
+### Secondary Screens
+
+- `/history`
+- `/settings`
+- `/admin`
+
+These screens are lower priority than the main voice loop and should be implemented after the core interaction path is stable.
+
+## Repository Layout
+
+- `apps/vela-ui` — minimal SvelteKit browser UI
+- `apps/vela-gateway` — minimal Fastify gateway service
+- `docs/` — technical documentation and phased backlog
+
+Use Yarn workspaces from the repository root to manage these packages.
+
+## Primary User Flow
+
+```text
+User presses mic
+→ audio streaming starts
+→ transcript appears
+→ final transcript sent
+→ assistant processes
+→ response streams as text and audio
+→ user can interrupt anytime
+```
+
+## Non-Goals for v1
+
+- full conversational memory system
+- emotion simulation or personality modeling
+- multi-user identity separation
+- offline LLM on the NanoPi
+- wake word and other future extensions listed in architecture docs
+
+## Documentation Map
+
+- [Architecture](architecture.md)
+- [Protocol](protocol.md)
+- [Integrations](integrations.md)
+- [Deployment](deployment.md)
+- [Setup](setup.md)
+- [Backlog](backlog.md)