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/backlog.md

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+# Vela Phased Backlog
+
+This backlog is the implementation plan translated into phased, actionable work. It should be updated whenever implementation changes scope, ordering, or done criteria.
+
+## Phase 1 — Foundation and Contracts
+
+### Goal
+
+Establish the boundaries, protocol, and state model for the system before integrating providers.
+
+### Backlog Items
+
+- [x] define repository structure for `vela-ui` and `vela-gateway`
+- define the WebSocket event contract used by the UI and gateway
+- define the session state machine and interrupt semantics
+- define provider adapter interfaces for STT, LLM, TTS, and tools
+- document error handling and cancellation behavior
+
+### Exit Criteria
+
+- protocol and state machine are documented
+- UI and gateway responsibilities are explicit
+- interrupt behavior is defined for every active phase
+- provider boundaries are clear enough to implement mocks first
+
+## Phase 2 — Vertical Slice Skeleton
+
+### Goal
+
+Prove the end-to-end interaction model with mocked or stubbed providers.
+
+### Backlog Items
+
+- [x] bootstrap `vela-ui` as a runnable SvelteKit app in the Yarn workspace
+- [x] bootstrap `vela-gateway` as a runnable Fastify app in the Yarn workspace
+- create a minimal UI with mic control, state indicator, transcript, and response text
+- create a gateway WebSocket session skeleton
+- implement mocked STT flow for partial and final transcript events
+- implement mocked LLM response streaming
+- implement stubbed audio playback or placeholder TTS output
+- implement interrupt handling across the mocked pipeline
+
+### Exit Criteria
+
+- one client can complete a voice turn through the real UI↔gateway contract
+- transcript appears in the UI
+- assistant text appears progressively or in structured steps
+- audio playback or stubbed playback is visible to the user
+- interrupt stops the active response and resets state cleanly
+
+## Phase 3 — Real STT Integration
+
+### Goal
+
+Replace the mocked transcription layer with a real streaming STT provider.
+
+### Backlog Items
+
+- integrate `whisper.cpp` behind the STT adapter
+- support partial and final transcript delivery
+- handle audio format conversion if browser capture format differs
+- handle late transcript events after cancellation
+- expose recoverable error handling for STT failures
+
+### Exit Criteria
+
+- live mic audio produces usable transcripts
+- partial and final results reach the UI
+- cancellation prevents late transcript results from corrupting session state
+- STT failure paths are visible and recoverable
+
+## Phase 4 — Ollama Streaming and Tool Calling
+
+### Goal
+
+Replace the mocked reasoning layer with real LLM orchestration.
+
+### Backlog Items
+
+- integrate Ollama behind the LLM adapter
+- stream assistant text deltas to the UI
+- define and validate tool-calling schema
+- reject invalid or unsafe tool calls
+- support interrupt during active thinking
+
+### Exit Criteria
+
+- assistant responses stream from Ollama
+- invalid tool requests fail safely
+- cancellation stops active model work
+- the LLM cannot directly execute external actions
+
+## Phase 5 — Tool Layer
+
+### Goal
+
+Introduce useful tools in increasing order of operational risk.
+
+### Backlog Items
+
+- implement SearXNG search adapter
+- normalize search results for LLM consumption
+- implement Home Assistant read actions
+- implement Home Assistant write actions gated by confirmation
+- implement clarification flow for ambiguous tool requests
+
+### Exit Criteria
+
+- web search works end-to-end
+- Home Assistant read queries work for approved entities
+- Home Assistant write actions require explicit confirmation
+- ambiguous actions do not execute automatically
+
+## Phase 6 — Kokoro TTS
+
+### Goal
+
+Convert assistant text responses into spoken output.
+
+### Backlog Items
+
+- integrate Kokoro behind the TTS adapter
+- support streamed audio when practical
+- add a temporary fallback for full-response playback if streaming is not ready
+- stop or suppress playback correctly on interrupt
+
+### Exit Criteria
+
+- spoken output plays in the UI
+- interrupt stops or suppresses playback reliably
+- any non-streaming fallback is explicitly documented as temporary
+
+## Phase 7 — Resilience and Performance
+
+### Goal
+
+Make the system robust enough for routine use on the target hardware.
+
+### Backlog Items
+
+- handle disconnect and reconnect cleanly
+- add bounded timeouts for STT, LLM, tool, and TTS calls
+- measure latency by pipeline stage
+- improve buffering and recovery paths for flaky network dependencies
+- validate behavior under cancellation and partial failure
+
+### Exit Criteria
+
+- common network and provider failures do not leave sessions stuck
+- latency is measurable at each major stage
+- user-visible recovery paths exist for expected failure modes
+
+## Phase 8 — Productization and Secondary Surfaces
+
+### Goal
+
+Polish the system after the core voice loop is reliable.
+
+### Backlog Items
+
+- add PWA installability and UX polish
+- implement `/history`
+- implement `/settings`
+- implement `/admin`
+- document operational settings and maintenance guidance
+
+### Exit Criteria
+
+- the app is installable as a PWA
+- secondary screens exist without degrading the core voice loop
+- supporting docs reflect the implemented behavior
+
+## Ongoing Documentation Tasks
+
+- update docs whenever implementation changes the protocol, architecture, integrations, deployment, or backlog order
+- mark completed backlog items or split phases into smaller slices as work progresses
+- keep root `README.md` as the entrypoint and keep detailed technical docs in `docs/`
+
+## Current Progress Notes
+
+- `apps/vela-ui` now boots as a minimal SvelteKit app with a starter page
+- `apps/vela-gateway` now boots as a minimal Fastify app with `/` and `/health` endpoints
+- backend framework choice is now concrete: Fastify