Add a 9Router-side proxy so the Headroom dashboard and its data
endpoints (/stats, /health, /stats-history, /transformations/feed)
stay same-origin when opened remotely through the 9Router app, and
add an "Open Headroom Dashboard" link in the Token Saver modal.
Gate /api/headroom/proxy as LOCAL_ONLY (loopback + CLI token) to
match start/stop, and strip cookie/authorization when the Headroom
target is non-loopback to avoid leaking viewer credentials.
Co-authored-by: Cursor <cursoragent@cursor.com>