feat: Add Mantine theme, 12 atom components, and 25 molecule components with Storybook stories

- Mantine theme with component extensions (Badge, Card, Paper, Button, etc.)
- CSS custom properties for design tokens (--inspector-* vars)
- Dark/light mode support with auto detection
- 12 atoms: StatusIndicator, AnnotationBadge, CapabilityItem, LogEntry,
  ProgressDisplay, ContentViewer, ListChangedIndicator, CopyButton,
  ConnectionToggle, TransportBadge, InlineError, MessageBubble
- 25 molecules: ServerCard, AddServerMenu, SchemaForm, ToolListItem,
  ToolDetailPanel, ResultPanel, ResourceListItem, ResourcePreviewPanel,
  ResourceTemplateInput, PromptArgumentsForm, PromptMessagesDisplay,
  LogControls, TaskCard, HistoryEntry, ServerInfoContent, ServerSettingsForm,
  RootsTable, SamplingRequestPanel, ElicitationFormPanel, ElicitationUrlPanel,
  InlineSamplingRequest, InlineElicitationRequest, PendingClientRequests,
  ImportServerJsonPanel, ExperimentalFeaturesPanel
- Exclude storybook-static from version control
- Exclude .stories.tsx from app tsconfig (Storybook-only modules)

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

clients/web/src/components/atoms/MessageBubble/MessageBubble.tsx

@@ -0,0 +1,44 @@
+import { Image, Paper, Stack, Text } from '@mantine/core';
+
+export interface MessageBubbleProps {
+  index: number;
+  role: 'user' | 'assistant';
+  content: string;
+  imageContent?: { data: string; mimeType: string };
+  audioContent?: { data: string; mimeType: string };
+}
+
+export function MessageBubble({
+  index,
+  role,
+  content,
+  imageContent,
+  audioContent,
+}: MessageBubbleProps) {
+  return (
+    <Paper p="md" radius="md" withBorder>
+      <Stack gap="xs">
+        <Text size="xs" c="dimmed">
+          [{index}] role: {role}
+        </Text>
+        <Text size="sm">&quot;{content}&quot;</Text>
+        {imageContent && (
+          <Image
+            src={`data:${imageContent.mimeType};base64,${imageContent.data}`}
+            maw={300}
+            radius="sm"
+            mt="xs"
+          />
+        )}
+        {audioContent && (
+          <audio controls>
+            <source
+              src={`data:${audioContent.mimeType};base64,${audioContent.data}`}
+              type={audioContent.mimeType}
+            />
+          </audio>
+        )}
+      </Stack>
+    </Paper>
+  );
+}