feat: add source badge to LogViewer entries

LogEntry now accepts an optional `source` field. When present, a small
badge (container/app/agent) renders between the level and message columns.
Backward compatible — entries without source render as before.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/design-system/composites/LogViewer/LogViewer.module.css

@@ -61,6 +61,38 @@
   background: color-mix(in srgb, var(--text-faint) 8%, transparent);
 }
 
+.sourceBadge {
+  flex-shrink: 0;
+  font-size: 9px;
+  font-family: var(--font-mono);
+  padding: 1px 6px;
+  border-radius: 3px;
+  line-height: 1.5;
+  white-space: nowrap;
+  min-width: 48px;
+  text-align: center;
+}
+
+.sourceContainer {
+  color: var(--text-muted);
+  background: color-mix(in srgb, var(--text-muted) 10%, transparent);
+}
+
+.sourceApp {
+  color: var(--running);
+  background: color-mix(in srgb, var(--running) 10%, transparent);
+}
+
+.sourceAgent {
+  color: var(--warning);
+  background: color-mix(in srgb, var(--warning) 10%, transparent);
+}
+
+.sourceDefault {
+  color: var(--text-muted);
+  background: color-mix(in srgb, var(--text-muted) 8%, transparent);
+}
+
 .message {
   font-size: 12px;
   font-family: var(--font-mono);

src/design-system/composites/LogViewer/LogViewer.test.tsx

@@ -3,9 +3,9 @@ import { render, screen } from '@testing-library/react'
 import { LogViewer, type LogEntry } from './LogViewer'
 
 const entries: LogEntry[] = [
-  { timestamp: '2024-01-15T10:30:00Z', level: 'info', message: 'Server started' },
-  { timestamp: '2024-01-15T10:30:05Z', level: 'warn', message: 'High memory usage' },
-  { timestamp: '2024-01-15T10:30:10Z', level: 'error', message: 'Connection failed' },
+  { timestamp: '2024-01-15T10:30:00Z', level: 'info', message: 'Server started', source: 'app' },
+  { timestamp: '2024-01-15T10:30:05Z', level: 'warn', message: 'High memory usage', source: 'container' },
+  { timestamp: '2024-01-15T10:30:10Z', level: 'error', message: 'Connection failed', source: 'agent' },
   { timestamp: '2024-01-15T10:30:15Z', level: 'debug', message: 'Query executed in 3ms' },
   { timestamp: '2024-01-15T10:30:20Z', level: 'trace', message: 'Entering handleRequest()' },
 ]
@@ -52,6 +52,23 @@ describe('LogViewer', () => {
     expect(el.classList.contains('custom-class')).toBe(true)
   })
 
+  it('renders source badges when source is provided', () => {
+    render(<LogViewer entries={entries} />)
+    expect(screen.getByText('app')).toBeInTheDocument()
+    expect(screen.getByText('container')).toBeInTheDocument()
+    expect(screen.getByText('agent')).toBeInTheDocument()
+  })
+
+  it('omits source badge when source is not provided', () => {
+    const noSourceEntries: LogEntry[] = [
+      { timestamp: '2024-01-15T10:30:00Z', level: 'info', message: 'No source here' },
+    ]
+    render(<LogViewer entries={noSourceEntries} />)
+    expect(screen.getByText('No source here')).toBeInTheDocument()
+    expect(screen.queryByText('app')).not.toBeInTheDocument()
+    expect(screen.queryByText('container')).not.toBeInTheDocument()
+  })
+
   it('has role="log" for accessibility', () => {
     render(<LogViewer entries={entries} />)
     expect(screen.getByRole('log')).toBeInTheDocument()

src/design-system/composites/LogViewer/LogViewer.tsx

@@ -5,6 +5,7 @@ export interface LogEntry {
   timestamp: string
   level: 'info' | 'warn' | 'error' | 'debug' | 'trace'
   message: string
+  source?: string
 }
 
 export interface LogViewerProps {
@@ -21,6 +22,12 @@ const LEVEL_CLASS: Record<LogEntry['level'], string> = {
   trace: styles.levelTrace,
 }
 
+const SOURCE_CLASS: Record<string, string> = {
+  container: styles.sourceContainer,
+  app: styles.sourceApp,
+  agent: styles.sourceAgent,
+}
+
 function formatTime(iso: string): string {
   try {
     return new Date(iso).toLocaleTimeString('en-GB', {
@@ -67,6 +74,11 @@ export function LogViewer({ entries, maxHeight = 400, className }: LogViewerProp
           <span className={[styles.levelBadge, LEVEL_CLASS[entry.level]].join(' ')}>
             {entry.level.toUpperCase()}
           </span>
+          {entry.source && (
+            <span className={[styles.sourceBadge, SOURCE_CLASS[entry.source] ?? styles.sourceDefault].join(' ')}>
+              {entry.source}
+            </span>
+          )}
           <span className={styles.message}>{entry.message}</span>
         </div>
       ))}