feat(kernel): KRNBUG-XAM-001 — XGetAVPack returns 8 (HDMI), not 0x16

Mirrors canary's cvars::avpack default (xam_info.cc:35) and Sylpheed's
accepted set {3,4,6,8} (xam_info.cc:250-251). With KRNBUG-XEX-001 having
flipped the priv-10 gate, XGetAVPack now reaches its caller in
sub_824AB578; returning 0x16 caused Sylpheed to abort the AV/crypto
block before XeCryptSha. Cascade walks one step (canary-only export
list 11 → 10); sub_824ABA98 is the next candidate.

Tests: 589 → 590. Goldens re-baselined (n50m: 50000005→50000004,
imports 407417→407416). Lockstep deterministic across 3 reruns at
-n 100M (instructions=100000010, import_calls=987686 +2.4×, swaps=2).
9-PC producer probe still 0×; parked handles 0x1004/0x100c/0x15e0
still signal_attempts=0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/xenia-app/tests/golden/sylpheed_n50m.json

@@ -1,6 +1,6 @@
 {
-  "instructions": 50000005,
-  "imports": 407417,
+  "instructions": 50000004,
+  "imports": 407416,
   "unimpl": 0,
   "draws": 0,
   "swaps": 2,