M1 progress: engine port compiles except pf.c; AF_DIVERT socket family; ifq framework

- compat layer extended through the full BSD API surface pf_ioctl/pf_lb/
  pf_if/pf_norm/pf_table/pf_ruleset/radix/md5/sha2 need (all compile):
  cpumem/counters model, ifaddr/ifg groups, cred view, endian+in6 names,
  NAT46/64, SipHash24, mbuf_list, frag6 helpers, ip6 forward/checksum,
  tcp options/FSM names, taskqueue & sysctl shims (documented in
  docs/porting-notes.md)
- pfsrc/divert_sock.c: real BSD divert(4) as runtime-registered PF_DIVERT=32
  socket family inside the module (sock_register; NPROTO=AF_MAX=45 -> zero
  core patches); divert_packet/divert6_packet wired for pf.c
- compat/pfk_ifq.c: OpenBSD 8.0 ifq framework with priq back end; hfsc and
  fq_codel aliases pending M5 (recorded in feature matrix as pending)
- design + plan updated for the divert decision (user-requested)
- stage-port.sh: single deterministic rename program for headers and .c

module/include/compat/crypto/siphash.h

@@ -20,8 +20,10 @@ typedef struct {
 
 void SipHash24_Init(SIPHASH_CTX *ctx, const SIPHASH_KEY *key);
 void SipHash24_Update(SIPHASH_CTX *ctx, const void *in, __u64 inlen);
-void SipHash24_Final(SIPHASH_CTX *ctx, unsigned char *out);
+void SipHash24_Final(void *out, SIPHASH_CTX *ctx);
 void SipHash24_Generate(const SIPHASH_KEY *key, const void *in, __u64 inlen,
 	unsigned char *out);
+/* OpenBSD's one-shot helper: returns the 64-bit hash value */
+__u64 SipHash24(const SIPHASH_KEY *key, const void *in, __u64 inlen);
 
 #endif