fix(frank-archon): :" guard needs a space — :"${VAR:?}"` runs :204800

The TTM_TARGET_MIB guard I added on 1a6a78e was written `:"...` (no space), so
bash parsed the expansion as one word and executed `cmd :204800` as the
command `:204800`: exit 127 `command not found` on every start, before the
ttm gate ran. Caught on the deploy: the unit crash-looped 34 times in ~4 min
with exactly that journal line.

probe-frank-archon-kv.py now reads the slot count, window and KV dtype from the
deployed env on the host, so probe B exercises the capacity contract that is
actually live (4 x 200,000 today) instead of a hardcoded pair, and each probe's
marker starts with a unique word because show() scores the hit on that word.

scripts/serve-frank-archon.sh

@@ -62,7 +62,7 @@ set +a
 : "${FRANK_ARCHON_PREFIX_DISK_MIB:?FRANK_ARCHON_PREFIX_DISK_MIB must be set}"
 : "${FRANK_ARCHON_NGRAM_PLACEMENT:?FRANK_ARCHON_NGRAM_PLACEMENT must be set}"
 : "${FRANK_ARCHON_TTM_MIN_MIB:?FRANK_ARCHON_TTM_MIN_MIB must be set}"
-:"${FRANK_ARCHON_TTM_TARGET_MIB:?FRANK_ARCHON_TTM_TARGET_MIB must be set}"
+: "${FRANK_ARCHON_TTM_TARGET_MIB:?FRANK_ARCHON_TTM_TARGET_MIB must be set}"
 : "${FRANK_ARCHON_RAD_MIN_MIB:?FRANK_ARCHON_RAD_MIN_MIB must be set}"
 
 # The image gate is the digest-pinned ref itself: a name@sha256 ref exists