feat(snapshots): Add is_selective column to PreprodSnapshotMetrics

Adds a boolean field to track whether a snapshot build was produced
by selective testing. Used to prevent selective builds from being
selected as baselines for comparison.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: NicoHinderling

src/sentry/preprod/migrations/0028_add_images_skipped_to_snapshot_comparison.py

@@ -1,7 +1,7 @@
 # Generated by Django 5.2.12 on 2026-04-14 21:31
 
 import sentry.db.models.fields.bounded
-from django.db import migrations
+from django.db import migrations, models
 
 from sentry.new_migrations.migrations import CheckedMigration
 
@@ -33,4 +33,9 @@ class Migration(CheckedMigration):
                 default=0, db_default=0
             ),
         ),
+        migrations.AddField(
+            model_name="preprodsnapshotmetrics",
+            name="is_selective",
+            field=models.BooleanField(default=False, db_default=False),
+        ),
     ]

src/sentry/preprod/snapshots/models.py

@@ -21,9 +21,7 @@ class PreprodSnapshotMetrics(DefaultFieldsModel):
     )
 
     image_count = BoundedPositiveIntegerField(default=0)
-
-    # Other future fields like carry forward references (selective testing),
-    # history support, etc.
+    is_selective = models.BooleanField(default=False, db_default=False)
 
     # Miscellaneous fields that we don't need columns for, e.g. enqueue/dequeue times, user-agent, etc.
     extras = models.JSONField(null=True)