chore(webapp): drop unused exports flagged by knip

RUN_COLUMN_IDS, STANDARD_COLUMNS, SMART_COLUMN_SOURCES, smartColumnRef and RunColumnGate are only used within runColumns.ts, so un-export them to satisfy the knip check. The externally-consumed RunColumnId/SmartColumnSource types stay exported.

Author: ericallam

apps/webapp/app/components/runs/v3/runColumns.ts

@@ -7,7 +7,7 @@ import type { Prisma } from "@trigger.dev/database";
  *
  * The order of `RUN_COLUMN_IDS`/`STANDARD_COLUMNS` is the default column order.
  */
-export const RUN_COLUMN_IDS = [
+const RUN_COLUMN_IDS = [
   "id",
   "task",
   "status",