Slug URLs with uuid short id: guard the full-uuid case

For title-first URLs like /n/<slug>-<first 12 hex of uuid>, resolve the short id with a primary-key range (prefix + zeros .. prefix + f's) instead of LIKE on id::text, so the btree index is used. Gotcha: a full v4 uuid's last group is also exactly 12 hex digits, so a regex like (?:^|-)([0-9a-f]{12})$ silently matches old /n/<uuid> links and looks up the wrong prefix; try parsing as a full uuid first. On a short-id clash, prefer the row whose current slug matches the requested path, then fall back to the oldest, and 308 any non-canonical form to the current path. Also in zsh, never name a loop variable path: it is tied to $PATH and every command after it becomes 'command not found'.