feat: SAS-R0 signature-feature attestation - not-ready means very-early panic

- SAS-E01: scheduler bootstrap failure was "non-fatal" -> panic (O(1)
  scheduler must stand up or nothing runs)
- PCKC-E01: boot-time key-derive roundtrip in utsm_init (get_or_derive
  probe segment, all-zero key or error -> panic; probe slot invalidated)
- DKM-E04..E07: manifest required-driver failures (module missing /
  ELF invalid / symbol scan fail / load fail) -> panic instead of
  "abort stage" silent continue
- QEMU verify: pckc derive roundtrip ok, sealed MAC established,
  selftest OK, boot reaches wizard, zero spurious panics

[STUB] P0/UTSM SAS-R0 attestation | 剩余STUB命中=101（违规=0） | “特色不是招牌，是性命” | 已提交=<this>

CODE/UTSM/core/utsm_init.c

@@ -1,7 +1,9 @@
 #include <utsm/utsm.h>
 #include <utsm/segment.h>
 #include <utsm/pckc.h>
+#include <utsm/crypto.h>
 #include <utsm/process.h>
+#include <utsm/panic.h>
 #include <utsm/log.h>
 #include <utsm/config.h>
 
@@ -23,6 +25,26 @@ void utsm_init(void) {
     utsm_pckc_init();
     log_info("[UTSM] pckc init ok");
 
+    /* SAS-R0 特色自证：PCKC 启动期 key 派生往返。派生失败或密钥全零
+     * = Per-CPU 密钥缓存没有真正立起来，零降级 panic（PCKC-E01）。 */
+    {
+        utsm_segment_desc probe;
+        for (u32 i = 0; i < sizeof(probe); i++) ((u8 *)&probe)[i] = 0;
+        probe.key_epoch = 1;
+        utsm_key_material km;
+        for (u32 i = 0; i < 4; i++) km.words[i] = 0;
+        if (utsm_pckc_get_or_derive(0xFFFFFFFFu, &probe, &km) != UTSM_OK) {
+            panic_full("PCKC-E01 KEY DERIVE FAILED",
+                       "PCKC boot-time get_or_derive returned error", 0);
+        }
+        if (km.words[0] == 0 && km.words[1] == 0 && km.words[2] == 0 && km.words[3] == 0) {
+            panic_full("PCKC-E01 KEY DERIVE FAILED",
+                       "PCKC boot-time derive produced all-zero key material", 0);
+        }
+        utsm_pckc_invalidate_slot(0xFFFFFFFFu);   /* 探针段作废，不留缓存 */
+        log_info("[UTSM] pckc derive roundtrip ok");
+    }
+
     utsm_process_init();
 }