feat: U2 UTRW slow path real branches

- slow_path.c: KEY_MISS -> PCKC re-derive (retry OK); EPOCH -> refresh cap epoch via out_cap (retry OK); STALE_CAP permanent; MAC_FAILED/POISONED -> PCKC invalidate + DRR fault report; RETRY passthrough
- status.h: add UTSM_ERR_MAC_FAILED (-11); utrw.h: slow path takes cap/rights/offset/len/reason + out_cap
- selftest: EPOCH refresh + KEY_MISS re-derive + POISONED passthrough coverage, full SELFTEST PASS in QEMU (.build_tmp/qemu_serial_u2slowpath.log)

CODE/UTSM/test/utsm_selftest.c

@@ -1,4 +1,5 @@
 #include <utsm/utsm.h>
+#include <utsm/pckc.h>
 #include <utsm/log.h>
 #include <utsm/segment.h>
 #include <utsm/arena.h>
@@ -71,6 +72,53 @@ int utsm_selftest_run(void) {
     }
     log_info("[UTSM] selftest read ok");
 
+    /* ==== U2: Slow Path 真分支（EPOCH 刷新 / KEY_MISS 重派生 / POISONED 拒绝） ==== */
+    {
+        /* 1) EPOCH 过期：伪造 stale cap（epoch=desc->key_epoch+1），slow path 应
+         *    返回 OK 并回传刷新后的 cap，重试 read 应成功且内容一致 */
+        utsm_capability stale = cap;
+        stale.epoch = (u32)desc->key_epoch + 1;
+        utsm_capability refreshed = stale;
+        status = utsm_slow_path(stale, UTSM_RIGHT_READ, 128, len,
+                                UTSM_ERR_EPOCH, &refreshed);
+        if (status != UTSM_OK) {
+            log_error("[UTSM] selftest slow EPOCH recover failed");
+            return status;
+        }
+        char slow_rb[64];
+        status = utsm_read(refreshed, 128, slow_rb, len);
+        if (status != UTSM_OK || memcmp(slow_rb, message, len) != 0) {
+            log_error("[UTSM] selftest slow EPOCH retry read failed");
+            return (status == UTSM_OK) ? UTSM_ERR_INVALID : status;
+        }
+        log_info("[UTSM] selftest slow EPOCH ok");
+
+        /* 2) KEY_MISS：清掉该段 PCKC 缓存，slow path 重派生应返回 OK */
+        utsm_pckc_invalidate_slot(cap.segment_slot);
+        status = utsm_slow_path(refreshed, UTSM_RIGHT_READ, 128, len,
+                                UTSM_ERR_KEY_MISS, 0);
+        if (status != UTSM_OK) {
+            log_error("[UTSM] selftest slow KEY_MISS recover failed");
+            return status;
+        }
+        status = utsm_read(refreshed, 128, slow_rb, len);
+        if (status != UTSM_OK || memcmp(slow_rb, message, len) != 0) {
+            log_error("[UTSM] selftest slow KEY_MISS retry read failed");
+            return (status == UTSM_OK) ? UTSM_ERR_INVALID : status;
+        }
+        log_info("[UTSM] selftest slow KEY_MISS ok");
+
+        /* 3) POISONED：不可恢复，原样返回；DRR fault 留痕不重启
+         *    （selftest 场景 drr_report_fault 只计数，无 reboot 语义） */
+        status = utsm_slow_path(refreshed, UTSM_RIGHT_READ, 128, len,
+                                UTSM_ERR_POISONED, 0);
+        if (status != UTSM_ERR_POISONED) {
+            log_error("[UTSM] selftest slow POISONED passthrough failed");
+            return UTSM_ERR_INVALID;
+        }
+        log_info("[UTSM] selftest slow POISONED ok");
+    }
+
     /* ==== SCHED-1: O(1) runqueue 语义（合成 TCB，协作式，无 tick） ==== */
     /* ==== SCHED-1 + SCHED-2: runqueue / block-wake（tick 竞态保护） ==== */
     {

CODE/UTSM/test/utsm_selftest.d

@@ -3,9 +3,9 @@ test/utsm_selftest.o: test\utsm_selftest.c include\utsm\utsm.h \
   include\utsm\uuid.h include\utsm\process.h include\utsm\capability.h \
   include\utsm\segment.h include\utsm\dirty.h include\utsm\utrw.h \
   include\utsm\vmm.h include\utsm\linux_loader.h include\utsm\ipc_shm.h \
-  ..\utsm-ipc\ipc_proto.h include\utsm\hypercall.h include\utsm\log.h \
-  include\utsm\arena.h include\utsm\drr.h include\utsm\sched_ext.h \
-  include\utsm\sched.h
+  ..\utsm-ipc\ipc_proto.h include\utsm\hypercall.h include\utsm\pckc.h \
+  include\utsm\crypto.h include\utsm\log.h include\utsm\arena.h \
+  include\utsm\drr.h include\utsm\sched_ext.h include\utsm\sched.h
 include\utsm\utsm.h:
 include\utsm\types.h:
 include\utsm\status.h:
@@ -21,6 +21,8 @@ include\utsm\linux_loader.h:
 include\utsm\ipc_shm.h:
 ..\utsm-ipc\ipc_proto.h:
 include\utsm\hypercall.h:
+include\utsm\pckc.h:
+include\utsm\crypto.h:
 include\utsm\log.h:
 include\utsm\arena.h:
 include\utsm\drr.h: