Limit log pattern examples to 100 in side panel (#1990)

## Problem

When a log pattern has thousands of sample events with large payloads, the `PatternSidePanel` renders all of them at once via `RawLogTable`, causing the page to freeze (HDX-3838).

The root cause: up to 10,000 samples are fetched and grouped by pattern. A single pattern can accumulate thousands of rows, and passing all of them to `RawLogTable` at once causes excessive DOM rendering.

## Solution

Limit the initial display in `PatternSidePanel` to **100 sample events**. If a pattern has more than 100 samples, a "Show all N samples" button is rendered below the table to let users load the full set on demand.

### Changes in `packages/app/src/components/PatternSidePanel.tsx`:
- Added `INITIAL_LIMIT = 100` constant and `showAll` state
- `displayedSamples` memo slices `pattern.samples` to the first 100 unless the user clicks "Show all"
- Reset `showAll` to `false` when the `pattern` prop changes (user selects a different pattern)
- Added a subtle Mantine `Button` below the table when there are more than 100 samples


Linear Issue: [HDX-3838](https://linear.app/clickhouse/issue/HDX-3838/investigate-issues-with-large-log-payloads-causing-problems)

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Co-authored-by: Cursor Agent <199161495+cursoragent@users.noreply.github.com>

Author: MikeShi42

packages/app/src/components/PatternSidePanel.tsx

@@ -1,7 +1,7 @@
 import * as React from 'react';
 import { JSDataType } from '@hyperdx/common-utils/dist/clickhouse';
 import { SourceKind, TSource } from '@hyperdx/common-utils/dist/types';
-import { Card, Drawer, Stack, Text } from '@mantine/core';
+import { Button, Card, Drawer, Stack, Text } from '@mantine/core';
 
 import DBRowSidePanel from '@/components/DBRowSidePanel';
 import { RawLogTable } from '@/components/DBRowTable';
@@ -92,6 +92,20 @@ export default function PatternSidePanel({
     [getRowWhere],
   );
 
+  const INITIAL_LIMIT = 100;
+  const [showAll, setShowAll] = React.useState(false);
+
+  React.useEffect(() => {
+    setShowAll(false);
+  }, [pattern]);
+
+  const displayedSamples = React.useMemo(() => {
+    if (showAll || pattern.samples.length <= INITIAL_LIMIT) {
+      return pattern.samples;
+    }
+    return pattern.samples.slice(0, INITIAL_LIMIT);
+  }, [pattern.samples, showAll]);
+
   const handleCloseRowSidePanel = React.useCallback(() => {
     setSelectedRowWhere(null);
   }, []);
@@ -126,7 +140,7 @@ export default function PatternSidePanel({
                   ~{pattern.count?.toLocaleString()} Sample Events
                 </Card.Section>
                 <RawLogTable
-                  rows={pattern.samples}
+                  rows={displayedSamples}
                   generateRowId={row => ({ where: row.id, aliasWith: [] })}
                   displayedColumns={displayedColumns}
                   columnTypeMap={columnTypeMap}
@@ -136,6 +150,17 @@ export default function PatternSidePanel({
                   showExpandButton={false}
                   isLive={false}
                 />
+                {!showAll && pattern.samples.length > INITIAL_LIMIT && (
+                  <Button
+                    variant="subtle"
+                    fullWidth
+                    size="xs"
+                    mt="xs"
+                    onClick={() => setShowAll(true)}
+                  >
+                    Show all {pattern.samples.length.toLocaleString()} samples
+                  </Button>
+                )}
               </Card>
             </Stack>
           </DrawerBody>