feat: backend gate fallback + metric_diff docs + submit_sft fix

- Auto-inject human-review gate when agent asks question but forgets gate entry
- Add complex_dev/complex_base field docs to program.md metric_diff table
- Fix submit_sft.sh minor issues
- jupyter_runtime improvements

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/app/components/assistant-ui/thread.tsx

@@ -1926,6 +1926,9 @@ function SkillInsertDialog() {
 								className="min-w-0 flex-1 text-left"
 								onClick={() => {
 									insertComposerText(`Use the ${skill.name} skill.\n\n`);
+									if (skill.name === "model-iteration") {
+										dispatchSkillToggled({ skill: skill.name, enabled: true });
+									}
 									setOpen(false);
 								}}
 							>