feat(frank-dragoon): halogen-flash-server 0.16.2 -> 0.18.20, NPU lane re-pinned

The engine pin moves to the newest vendor release (0.18.20, image built
2026-10-30). The payload lock is the gate this deploy has to pass: the v2
.hgn loads only in the flash-server line, so /health plus the boot ledger
decide, and the rollback is the 0c61bf84 digest on the same env line.

0.18.20's NPU catalog is NOT the 0.16.2 one: it names 14 device programs
(u0..u13) and an 8,495,512 B consts.hnpb where 0.16.2 had 10 and 5,086,496 B,
and the entrypoint verifies size+sha256 for every staged file before it
starts. HALOGEN_NPU_MODELS names qwen3-embedding-0.6b, so the staging set is
re-pinned to revision 8fd44c9f with the new block — bumping the engine alone
would refuse the boot on the NPU lane.

tests/frank_dragoon_unit.bats

@@ -1,7 +1,7 @@
 #!/usr/bin/env bats
 # Seam: frank-dragoon serves Quat3rnion's NATIVE v2 conversion (2026-10-11)
 # of the abliterated Qwen3.8-Flash-Next (a .hgn flash-server payload) on the
-# Strix Halo iGPU through the halogen-flash-server CONTAINER (0.16.2,
+# Strix Halo iGPU through the halogen-flash-server CONTAINER (0.18.20,
 # digest-pinned), driven by the root unit's serve script — 2 slots over ONE
 # 401,408-position KV pool at the native 262,144 ceiling, MTP head always on (HALOGEN_SPEC_ADAPT=0)
 # and the vision tower mounted. 2026-10-17 cutover from the Swift1.5-finetune