Live testing hit `entities_slug_key` violations: exec slugs used an 8-char
prefix of a UUIDv7, whose leading bytes encode a millisecond timestamp — two
executions created seconds apart can share a prefix. Use the full UUID
(guaranteed unique) for the exec entity's slug/name in request_execution, the
new `run` tool, and the REST RequestExecution handler — all three had the
same pattern.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>