Replicates `TaskRun.planType` into the `task_runs_v2` ClickHouse table
so run analytics can group by plan type.
Adds a `plan_type` column (goose migration `033`,
`LowCardinality(String)`), the replication insert mapping, and the
matching schema/column/type entries - same shape as the recent `region`
addition. Write-once at trigger, so it just rides along on existing
replicated rows. Internal analytics only; not exposed in the Query API.
nicktrn
6bdf800a11