frank-default-large: full native 262144 context per slot (524288 total)

llama.cpp splits -c across -np slots; to give each of the 2 slots the full
262144 native context, set CTX_SIZE=524288. KV ~32 GiB; fits the 96 GiB
unified pool. Update env default, serve-script fallback, and the deployment
doc line.

scripts/serve-frank-large.sh

@@ -37,7 +37,7 @@ fi
 : "${ALIAS:=frank-default-large}"
 : "${BIND_ADDR:=0.0.0.0}"
 : "${LISTEN_PORT:=52625}"
-: "${CTX_SIZE:=262144}"
+: "${CTX_SIZE:=524288}"
 : "${PARALLEL:=2}"
 : "${BATCH_SIZE:=2048}"
 : "${UBATCH_SIZE:=2048}"