CDN-218: The c/f Evidence Hunt

CDN-218 audits the public evidence that could open the first TRAPPIST-1 TTY mode after CDN-217. Agol et al. 2024 already publish c and f JWST timings, with c=5 and f=5, and CDN-212 matches those rows to the published N-body forecast table. But the same timings are reused inside the published fitted null, so they remain diagnostic evidence rather than an independent TTY payment. Allen/GO-6456 is external and public, but contains b/d/e timing checks and no c/f row. Therefore public c/f evidence exists, while gate-eligible c/f evidence remains zero.