lith Caddy: redirect /platter/jeffrey to trailing-slash form
The page at /platter/jeffrey (no slash) fetches `./manifest.json`,
which the browser resolves to /platter/manifest.json (treating
`jeffrey` as a file in /platter/, not a directory). That 404s into
the SPA fallback, returns HTML, and the dashboard's JSON.parse
errors with "Unexpected token '<'". Forcing the trailing-slash form
keeps the page's base URL aligned with what relative fetches expect.
Same pattern as the /platter redirect added in the previous commit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>