docs(arbo): GRANITE_KEY scope now granite + qwen-vision (extended)

The arbo-prompt-enhance vkey was extended to reach qwen3.5-9b-fp8 for the
hero auto-judge step (v0.11.3+), not granite-only. Confirmed via /v1/models
for the key. Docs-only; no version bump.

stacks/arbo/.env.example

@@ -20,7 +20,8 @@ ARBO_CATALOG_DIR=/worktank/arbo/repo
 #   Mint a fresh one:  openssl rand -hex 32
 ENGINE_TOKEN=
 
-# GRANITE_KEY: the LiteLLM virtual key scoped to arbo (granite-only).
-#   comfy-dev already holds 'arbo-prompt-enhance' (issued 2026-06-09) —
-#   reuse or rotate it; do NOT use the master sk-corvid key.
+# GRANITE_KEY: the LiteLLM virtual key scoped to arbo. The 'arbo-prompt-enhance'
+#   vkey (comfy-dev, issued 2026-06-09) is extended to reach BOTH granite-4.1-8b
+#   (gen step) AND qwen3.5-9b-fp8 (vision / hero judge step, v0.11.3+).
+#   Reuse or rotate it; do NOT use the master sk-corvid key.
 GRANITE_KEY=

stacks/arbo/README.md

@@ -34,9 +34,12 @@ the standard fleet pattern:
 - **`ENGINE_TOKEN`** — auth is **OPEN today**. Mint a real bearer
   (`openssl rand -hex 32`), put it in `.env`. Closing this is the one security
   fix the move buys us.
-- **`GRANITE_KEY`** — the LiteLLM **virtual key scoped to arbo** (granite-only).
-  comfy-dev already holds `arbo-prompt-enhance` (issued 2026-06-09); reuse or
-  rotate it. Never the master `sk-corvid`.
+- **`GRANITE_KEY`** — the LiteLLM **virtual key scoped to arbo**. The
+  `arbo-prompt-enhance` vkey (comfy-dev, issued 2026-06-09) was **extended**
+  to reach **both** `granite-4.1-8b` (prompt-craft / `gen` step) **and**
+  `qwen3.5-9b-fp8` (vision / the hero auto-`judge` step, v0.11.3+) — `/v1/models`
+  for this key lists exactly those two. Reuse or rotate it; never the master
+  `sk-corvid`.
 
 ## Q4 — Volumes + backup