feat(explore): Enlarge chart size for explore Slack unfurls (#112697)

Increase the chart dimensions from the default 450x150 to 1600x1200 for
explore Slack unfurls. The small default size renders poorly in Slack,
especially in full screen view. Letting Slack handle the downsizing from
a larger source image produces much better results.

Only the explore unfurl is changed — all other chart types continue
using the default size.

Fixes DAIN-1491

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: DominikB2014

src/sentry/integrations/slack/unfurl/explore.py

@@ -12,7 +12,7 @@
 from sentry import analytics, features
 from sentry.api import client
 from sentry.charts import backend as charts
-from sentry.charts.types import ChartType
+from sentry.charts.types import ChartSize, ChartType
 from sentry.integrations.messaging.metrics import (
     MessagingInteractionEvent,
     MessagingInteractionType,
@@ -36,6 +36,8 @@
 DEFAULT_PERIOD = "14d"
 TOP_N = 5
 
+EXPLORE_CHART_SIZE: ChartSize = {"width": 1600, "height": 1200}
+
 
 class ExploreDatasetDefaults(TypedDict):
     title: str
@@ -152,7 +154,7 @@ def _unfurl_explore(
             chart_data["type"] = chart_type
 
         try:
-            url = charts.generate_chart(style, chart_data)
+            url = charts.generate_chart(style, chart_data, size=EXPLORE_CHART_SIZE)
         except RuntimeError:
             _logger.warning("Failed to generate chart for explore unfurl")
             continue