fix: final review pass — email collision, orphaned-run loop, null confidence guards

- changeEmail validates and refuses an address another account owns (users.email is UNIQUE; a collision was a 500 inside the settings form).
- /app/[id] no longer redirects a 'running' row to itself; it renders what exists and says the run was interrupted.
- ScoreBar / OptionRow / VerdictBlock survive null numbers from the model instead of throwing and losing the block (seen live: '[openui] runtime/render-error: Component ScoreBar render failed').
- drop the ad-hoc render-debug scripts now that Playwright covers the browser.

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

tests-e2e/responsive.spec.ts

@@ -19,7 +19,8 @@ test("every settings field has a visible label", async ({ page }) => {
   await page.goto("/settings");
   // Scoped to the form: the rail's rename boxes are labelled for assistive tech with aria-label, not visibly.
   const orphans = await page.evaluate(() => [...document.querySelectorAll("form input")]
-    .filter((i) => i.type !== "hidden" && (!i.id || !document.querySelector(`label[for="${i.id}"]`)))
-    .map((i) => i.name || i.type));
+    .filter((el) => { const i = el as HTMLInputElement;
+      return i.type !== "hidden" && (!i.id || !document.querySelector(`label[for="${i.id}"]`)); })
+    .map((el) => (el as HTMLInputElement).name || (el as HTMLInputElement).type));
   expect(orphans).toEqual([]);
 });