fix: 32-bit rshift broke QUIC pn recovery for 4-byte packet numbers

recover_packet_number halved pn_win with bit.rshift, which is 32-bit on
LuaJIT: for pn_len = 4, pn_win = 2^32 truncates to 0, so pn_hwin = 0 and
any retransmitted packet decoded to pn + 2^32 — wrong nonce, AEAD tag
mismatch. Halve with plain arithmetic (exact on doubles).

Also fix the stale uncompressed-IPv6 expectation in the openssl-backend
google-capture test (same issue as the kernel variant). Both paths only
run where libcrypto is available — first exercised by the CI runner.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: jperon

ipparse/l4/quic/v1/protection.moon

@@ -97,7 +97,9 @@ recover_packet_number = (truncated, expected, pn_len) ->
   pn_win = 1
   for _ = 1, pn_len * 8
     pn_win *= 2
-  pn_hwin = rshift pn_win, 1
+  -- pn_win can be 2^32 (pn_len = 4): bitops are 32-bit on LuaJIT, so halve
+  -- with plain arithmetic (exact on doubles).
+  pn_hwin = pn_win / 2
   candidate = (expected - (expected % pn_win)) + truncated
   if candidate <= expected - pn_hwin
     candidate + pn_win

ipparse/tests/l7/quic/test_google_capture_backends.moon

@@ -25,7 +25,7 @@ EXPECTED = {
   dst_mac: "f2198cc26bb3"
   src_mac: "f2e9008a2acc"
   src_ip:  "3ffa:e7fe:4375:16ed:e28f:4cff:fec8:91fa"
-  dst_ip:  "2485:ec87:7655:20de:0:0:0:8b"
+  dst_ip:  "2485:ec87:7655:20de::8b"  -- ip62s compresses zero runs (RFC 5952)
   udp_spt: 35336
   udp_dpt: 443
   sni: "google.com"