docs: publish Preview 19 dogfood evidence

Export the reviewed allowlisted snapshot from private source commit 05928cebd01b586cf9e9d4b8c8537a7605a6068c. This records the exact candidate, bounded capacity result, stateful migration scratch requirement, authenticated batch identity proof, and immediate live acceptance evidence.

AI-Assisted: OpenAI Codex
Signed-off-by: Cole Speelman <crspeelman@gmail.com>

internal/storage/batch_metadata.go

@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+
+package storage
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+)
+
+func migrateControlBatchMetadata(db *sql.DB) error {
+	tx, err := db.Begin()
+	if err != nil {
+		return errors.New("begin batch metadata migration")
+	}
+	defer tx.Rollback()
+	for _, statement := range []string{
+		`ALTER TABLE segments ADD COLUMN record_count INTEGER NOT NULL DEFAULT 0 CHECK(record_count BETWEEN 0 AND 5000)`,
+		`UPDATE schema_version SET version=10 WHERE version=9`,
+	} {
+		if _, err = tx.Exec(statement); err != nil {
+			return fmt.Errorf("migrate batch metadata: %w", err)
+		}
+	}
+	if err = tx.Commit(); err != nil {
+		return errors.New("commit batch metadata migration")
+	}
+	return nil
+}