Remove the Codex LLM review and the per-PR image job — both spent API
tokens on every Bossbot run and the connector review already covers
code review. The gate is now fully deterministic: Tests passed for the
head SHA, non-draft, trusted author, zero unresolved review threads.
Prompt/schema files removed; guard tests updated to forbid
openai/codex-action and image generation from reappearing.
Signed-off-by: phernandez <paul@basicmachines.co>