Attached IDA binds the open database to the target only through the
recorded whole-input SHA-256, path and image base. Every slice of a
universal Mach-O shares that digest, so an attached database of another
slice passed the identity check and its results were attributed to the
host-selected architecture. Attached admission now reports the target
format as unsupported, with lipo -thin and headless recovery, before any
upstream contact. Headless mode keeps thinning the selected slice.
Fixes#3871
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>