fix(parquet): RestoreNonColumnFields skips non-string tags instead of panicking

The tags-restore loop used an unchecked v.(string), so a stored extras tags array with a
non-string element ({"tags":[42]} or a null, from arbitrary producer JSON / a backfilled
bundle) panicked. The parquet Decode path has no recover, so this crashed the reader/backfill.
Comma-ok the element assertion: skip non-strings, keep strings in order. Identical for
well-formed input. Regression test added.

Author: zer0stars

field_accessors.go

@@ -29,9 +29,15 @@ func RestoreNonColumnFields(event *CloudEventHeader) {
 	}
 	if val, ok := event.Extras["tags"]; ok {
 		if anySlice, ok := val.([]any); ok {
-			typedSlice := make([]string, len(anySlice))
-			for i, v := range anySlice {
-				typedSlice[i] = v.(string)
+			// Skip non-string elements rather than panic on the unchecked assertion:
+			// stored extras come from arbitrary producer JSON (e.g. a backfilled bundle
+			// with {"tags":[42]} or a null element), and the parquet Decode path has no
+			// recover — an unguarded v.(string) would crash the reader/backfill.
+			typedSlice := make([]string, 0, len(anySlice))
+			for _, v := range anySlice {
+				if s, ok := v.(string); ok {
+					typedSlice = append(typedSlice, s)
+				}
 			}
 			event.Tags = typedSlice
 		}

field_accessors_panic_test.go

@@ -0,0 +1,20 @@
+package cloudevent
+
+import "testing"
+
+// TestRestoreNonColumnFields_MalformedTags: a stored tags array with non-string
+// elements (arbitrary producer JSON / a backfilled bundle) must not panic. Non-string
+// elements are skipped; strings are kept in order. Before the fix the unchecked
+// v.(string) panicked on the parquet Decode path, which has no recover.
+func TestRestoreNonColumnFields_MalformedTags(t *testing.T) {
+	hdr := &CloudEventHeader{
+		Extras: map[string]any{"tags": []any{"ok", float64(42), nil, "two", true}},
+	}
+	RestoreNonColumnFields(hdr) // must not panic
+	if len(hdr.Tags) != 2 || hdr.Tags[0] != "ok" || hdr.Tags[1] != "two" {
+		t.Fatalf("expected [ok two], got %v", hdr.Tags)
+	}
+	if _, stillThere := hdr.Extras["tags"]; stillThere {
+		t.Error("tags should be deleted from Extras after restore")
+	}
+}