feat: store verdict preview pages in repo-local ./tmp

Multi-day reviews need to survive reboots, which system /tmp does not
guarantee. ./tmp is git-ignored so the generated pages never land in
commits.

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

.gitignore

@@ -18,6 +18,7 @@ docs/*
 !docs/adr/
 
 # agents
+tmp/
 .superpowers/
 .playwright-cli/
 skills-lock.json