TIC 32636748 (LP 907-22): a candidate ultra-short-period planet in public TESS data

We report a periodic transit-like signal on the nearby K7 dwarf TIC 32636748 (LP 907-22, Tmag 10.44, d about 55 pc) in six sectors of public TESS data (2019-2026). The signal has a period of 0.7323249 +/- 0.0000005 d (17.58 h), a depth of 340 +/- 25 ppm and a duration of about 0.77 h, corresponding to a planet of about 1.3-1.6 Earth radii. It was found in a blind coherent multi-sector search of the three earliest sectors and recovered at the predicted ephemeris in three later sectors that did not enter the selection (held-out z = 9.2-9.7). Five AI-assisted re-analyses and refutation attempts (all Claude models, therefore not independent replications) did not refute the signal, and two critical manuscript reviews (the second with a different Claude model) reproduced it from public data; a retrospective forecast of the 2026 sectors from data up to 2025 was met but cannot be verified by third parties and was not strictly blind. Gaia radial velocities exclude an eclipsing binary containing the K7 star itself. The main open issue is a possible unresolved companion (Gaia RUWE 1.73) that could host a bound eclipsing binary; companions within about 10 arcsec are not excluded, and because the duration needs b about 0.8 on the K7 star but is natural for a bound M-dwarf companion, such a companion is at least as likely a host as the K7 star. The star has no TOI or CTOI. A falsifiable prediction for TESS Sector 114 (scheduled 13 Feb - 14 Mar 2027) is recorded with a pre-defined decision rule. This is an UNCONFIRMED planet candidate; the preprint has not been peer reviewed. The analysis was carried out with AI assistance (Claude, Anthropic); the author is responsible for the content. All data are public (MAST, Gaia DR3); the supplementary archive contains normalised light curves, figures, predicted transit times, the forecast file with its SHA-256 checksum, the evaluation script of the Sector 114 rule (with its SHA-256), scripts and the review reports.