MINT: parameterize with full name, username, email, phone

Extends user_identity_seed_t (version 2) with fixed-size full_name/
username/email/phone fields -- plenty of unused pad space (4016 bytes)
was already there. Deliberately NOT encoded into the DER cert's Subject
field: that would mean building a real X.509 RDNSequence (OIDs for
commonName/emailAddress, PrintableString/UTF8String tagging), well past
this project's own stated "deliberately not a general ASN.1/X.509
[builder]" scope. This human-readable profile data isn't
security-relevant the way pubkey/serial are (the only two fields
CERTVERIFY/BINDSTEP actually check) -- it travels alongside the keypair
in the plain identity record instead.

capsule_mint_identity() takes full_name/username (required, validated
non-empty and within their fixed field widths) and email/phone (NULL or
empty = null, matching the schema's own nullable convention). The MINT
FORTH word's stack signature grows to 4 string pairs
( fname-c fname-u uname-c uname-u email-c email-u phone-c phone-u -- ok? ).

Verified live in QEMU: minted two real identities with real profile
data -- Zuse (full_name "Konrad Suse", username "Zuse",
zuse@pantheon.org) onto disk/zuse.img, and a regular user (full_name
"Captain Bob", username "CaptBob", capt.bob@pantheon.org) onto
disk/user1.img -- then read the raw devblock bytes back off both images
directly and confirmed every field byte-exact at its correct struct
offset. Clean 3-architecture regression boot confirms no side effects.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019ZGkimpfyh63EZyRkNbkPD

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