When a polecat is nuked and re-spawned with the same name, CreateAgentBead
fails with a UNIQUE constraint error because the old agent bead exists as
a tombstone.
This adds CreateOrReopenAgentBead that:
1. First tries to create the agent bead normally
2. If UNIQUE constraint fails, reopens the existing bead and updates fields
Updated both spawn paths in polecat manager to use the new function.
Fixes#332
Co-authored-by: Claude <noreply@anthropic.com>