feat: ChatSources sidebar with grouped source links

CLAUDE.md

@@ -100,6 +100,8 @@ pnpm test             # Run tests
 | `ChatInput` | Message input form with submit handling |
 | `ChatToggleButton` | Floating button to open/close chat |
 | `MessageBubble` | Renders individual messages with URL linking |
+| `ChatSources` | Slide-out sidebar displaying grouped source links |
+| `SourceIcon` | Icon button with badge count to trigger source sidebar |
 
 ### useChat Hook
 
@@ -139,7 +141,10 @@ Manages chat state:
 
 // Response
 {
-  reply: "How can I help you today?"
+  reply: "How can I help you today?",
+  sources?: [
+    { url: "https://...", title: "...", type: "blog" | "page" | "external" }
+  ]
 }
 ```
 

docs/plans/2026-03-24-chat-sources-design.md

@@ -0,0 +1,99 @@
+# ChatSources Component Design
+
+**Issue:** #4 - Source and search results display component
+**Date:** 2026-03-24
+
+## Overview
+
+A slide-out sidebar panel that displays source links associated with assistant messages. Sources are returned by the worker API, grouped by type, and triggered via an icon button on each message.
+
+## Types
+
+```typescript
+interface Source {
+  url: string;
+  title: string;
+  type: "blog" | "page" | "external";
+}
+
+// ChatResponse expands:
+interface ChatResponse {
+  reply: string;
+  sources?: Source[];
+}
+
+// ChatMessage expands:
+interface ChatMessage {
+  id: string;
+  role: "user" | "assistant";
+  content: string;
+  sources?: Source[];
+}
+```
+
+## Components
+
+### SourceIcon (new)
+
+Trigger button displayed on assistant messages that have sources.
+
+- Small link/document icon, bottom-left of assistant message bubble
+- Tiny badge circle showing source count, colored `claudius-primary`
+- Muted by default, more visible on hover
+- Tooltip: "View sources"
+- Clicking toggles the ChatSources sidebar for that message
+
+### ChatSources (new)
+
+Slide-out sidebar panel.
+
+- Slides from the left edge of ChatWindow, overlaying the message area
+- Width: ~280px
+- Background: `claudius-light` (dark mode aware)
+- Border-right: 2px `claudius-border`
+- Rounded corners on right side
+- Smooth slide transition (~200ms ease)
+
+**Header:**
+- "Sources" title
+- "{n} sources found" subtext
+- Close (X) button
+
+**Body:**
+- Grouped by type: blogs first, then pages, then external
+- Type group headers: small muted labels ("Blog", "Page", "External"), only shown if that type has entries
+- Source cards: rounded-[12px], 2px border, subtle fill
+- Each card shows title (truncated) and domain extracted from URL
+- Click opens link in new tab
+- Hover: slight background shift
+
+**No empty state needed** - icon only appears when sources exist.
+
+## Integration
+
+### Files to create
+
+- `widget/src/components/ChatSources.tsx` - Sidebar panel
+- `widget/src/components/SourceIcon.tsx` - Trigger button with badge
+
+### Files to modify
+
+- `widget/src/api/types.ts` - Add `Source` type, update `ChatResponse`
+- `widget/src/hooks/useChat.ts` - Pass sources through to `ChatMessage`
+- `widget/src/components/MessageBubble.tsx` - Render SourceIcon for assistant messages with sources
+- `widget/src/components/ChatWindow.tsx` - Manage sidebar state, render ChatSources overlay
+- `widget/src/index.ts` - Export new types
+
+### Not in scope (this PR)
+
+- Worker changes to return source data. Widget will be built and testable with mock data in dev mode.
+
+## Filtering
+
+The worker handles domain filtering server-side using the client's `allowedDomains` config. The widget trusts and renders whatever sources the API returns.
+
+## Source grouping order
+
+1. Blog posts (`type: "blog"`)
+2. Site pages (`type: "page"`)
+3. External links (`type: "external"`)