docs: fix links to archived pre-reorg pages

Co-authored-by: nullun <git@nullun.com>
Co-authored-by: cce <51567+cce@users.noreply.github.com>

falcon_det{1024,512}_pubkey_coeffs skipped the first byte of the key and
decoded the remaining bytes without ever looking at it, so a buffer whose
header byte is wrong (a key for a different logn, or bytes that are not a
Falcon public key at all) was unpacked as though it were valid, returning 0
and a coefficient vector that does not correspond to any det key. The
verify entry points do not have this gap: they go through falcon_verify,
which checks the header before touching the rest of the key. Check the
byte here the same way and return FALCON_ERR_FORMAT, which the header's
"non-zero error code if pubkey is invalid" contract already promises.

deterministic1024.o and deterministic512.o were in the shared OBJ list, so
every binary linked both, including test_falcon and speed, which use
neither, and each KAT driver, which uses only its own variant. Give each
test_deterministic<n> binary its own deterministic<n>.o prerequisite and
keep the generic objects in OBJ, so a binary pulls in only the variant it
exercises. The objects still have their own rules and "clean" still
removes them.