fix(v4): MINT-ZUSE wipes Zuse's seed on every return, not only on success (#176, the mint)

sk_v4_mint_zuse wiped seed and rseed only when the real Zuse was minted; its
refusals and every failure after YES left them in stack memory.

Option 1 (Captain Bob, 2026-11-12: "1 is great"): the seeds are in a 64-byte
buffer the caller owns. sk_v4_mint_zuse_with(seeds) runs the mint (now a
private mint()) and then wipes the buffer, whichever way it returned -- one
place, every exit; sk_v4_mint_zuse() gives it a buffer of its own.

kernel/tests/test_sk_v4_mint.c, 17 checks: the real gpt.c on the RAM disk, the
identity code, key mint, signature checks, marker and keyboard faked; each of
the mint's eight exits run with the buffer filled with 0xEE first -- no stick,
under 64 MiB, not YES, the key mint failing, the read-back not hers, no
marker, the marker write failing, and minted. Against the mint as it was: 7
failures (every exit but success). Now: 0. Both runs in logs/20261112-181719/. Built for
amd64, aarch64, riscv64. The identity code's two (sk_v4_genesis,
sk_v4_real_zuse_arrived) follow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017RzZgrf7V7Zk2iczBXDRbm

kernel/include/starkernel/v4/sk_v4_mint.h

@@ -9,6 +9,8 @@
 #ifndef STARKERNEL_V4_SK_V4_MINT_H
 #define STARKERNEL_V4_SK_V4_MINT_H
 
+#include <stdint.h>
+
 /* The whole of STICK.md 6a's minting: asks for a stick, shows its size, writes
  * nothing until YES, then a GPT and a fresh Zuse identity on it, read back,
  * and only then the real key in the genesis marker. 0 when she is minted;
@@ -16,4 +18,8 @@
  * MINT-ZUSE word, and (Task 5) the fixed screen's R. */
 int sk_v4_mint_zuse(void);
 
+/* The same, with Zuse's seed and its read-back in `seeds` (64 bytes), owned by the caller: on every
+ * return the 64 bytes are zero (#176). */
+int sk_v4_mint_zuse_with(uint8_t seeds[64]);
+
 #endif /* STARKERNEL_V4_SK_V4_MINT_H */