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

include/starkernel/capsule_mint.h

@@ -39,6 +39,10 @@ typedef enum {
                                * assumed away). */
     MINT_ERR_WRITE_FAIL,     /* a devblock write failed partway through --
                                * the drive may be left partially minted. */
+    MINT_ERR_INVALID_PROFILE, /* full_name/username missing or too long for
+                               * user_identity_seed_t's fixed fields, or
+                               * email/phone too long (both may be NULL/empty
+                               * -- that's "null", not invalid). */
 } MintResult;
 
 /**
@@ -54,9 +58,16 @@ typedef enum {
  * @param dev        Already-open block device for the target drive.
  * @param issuer_vm  The signing identity -- in practice always Hera's own
  *                   VM (Zuse's cert lives there, vm.h's zuse_cert_seed).
+ * @param full_name  Required, NUL-terminated, fits user_identity_seed_t's
+ *                   full_name field (§F.20).
+ * @param username   Required, NUL-terminated, fits its username field.
+ * @param email      NULL or empty string = null (field stays empty).
+ * @param phone      NULL or empty string = null (field stays empty).
  * @return MINT_OK on success, an error code otherwise.
  */
-MintResult capsule_mint_identity(struct blkio_dev *dev, VM *issuer_vm);
+MintResult capsule_mint_identity(struct blkio_dev *dev, VM *issuer_vm,
+                                  const char *full_name, const char *username,
+                                  const char *email, const char *phone);
 
 #endif /* __STARKERNEL__ */