# Issue #20 — Error handling and connection status

**Status: COMPLETED**

## Overview
Global error boundary, toast notifications for gRPC errors, connection status indicator, and retry logic with exponential backoff.

## Implemented Components

### Toast System
- **`src/lib/stores/toast.svelte.ts`** — Svelte 5 runes-based toast store with `addToast`, `removeToast`, `clear`. Auto-dismiss with configurable durations (5s for success/info, 10s for errors, 8s for warnings).
- **`src/lib/components/ToastContainer.svelte`** — Fixed bottom-right toast stack. Color-coded by type (red/amber/green/blue) with icons, dismiss buttons, and full dark mode support.

### Connection Status
- **`src/lib/stores/connection.svelte.ts`** — Tracks gRPC connection state (`connected` / `reconnecting` / `disconnected`) based on consecutive failures.
- **`src/lib/components/ConnectionStatus.svelte`** — Header indicator with colored dot (green/amber-pulse/red) and label. Dark mode support.

### Retry Logic
- **`src/lib/services/orchestrator.ts`** — Added:
  - Exponential backoff retry (up to 3 retries) for transient gRPC codes (`UNAVAILABLE`, `DEADLINE_EXCEEDED`, `ABORTED`, `INTERNAL`).
  - `friendlyMessage()` mapper from gRPC codes to user-friendly strings.
  - Connection store integration (reports success/failure).
  - Toast notifications on errors.

### Error Boundary
- **`src/routes/+error.svelte`** — Global SvelteKit error page with status code, friendly message, and "Go back" / "Try again" / "Home" buttons. Full dark mode support.

### Integration
- **`src/routes/+layout.svelte`** — Added `ToastContainer` to global layout.
- **`src/routes/chat/+page.svelte`** — Added `ConnectionStatus` in header, "Retry" button on failed requests, toast notifications on errors, user-friendly error messages.

## Files Changed
| File | Change |
|------|--------|
| `src/lib/stores/toast.svelte.ts` | New |
| `src/lib/stores/connection.svelte.ts` | New |
| `src/lib/components/ToastContainer.svelte` | New |
| `src/lib/components/ConnectionStatus.svelte` | New |
| `src/routes/+error.svelte` | New |
| `src/lib/services/orchestrator.ts` | Modified — retry, friendly messages, store integration |
| `src/routes/+layout.svelte` | Modified — added ToastContainer |
| `src/routes/chat/+page.svelte` | Modified — ConnectionStatus, Retry button, toast integration |
| `implementation-plans/issue-020.md` | New |
| `implementation-plans/_index.md` | Modified |