llm(frank-archon): claim the card's settling slack, slab 24000 -> 25600

The 2 GiB/card that \`rocm-smi\` shows free is not idle: the engine's budget
table calls it driver context + the 896 MiB activation arena + 96 MiB headroom,
and says the rest is `throughput on the floor`. Its own settle line is the
number that matters — `card 0 settled at 2.01 GiB free against 209.19 MiB (the
96.00 MiB --gpu-headroom-mib and 113.19 MiB kept for the static region)` — so
1,849 MiB above the ENGINE's floor is claimable and the real ceiling is 30,969
MiB, not the 29,120 my 1 GiB reserve invented on 2026-10-11.

Shipped pair 25600/5120 = 30,720: +1,600 MiB of slab, ~458 MiB above the floor.
The slab is already saturated at 24,000 (mover took all of it, 451 KiB slack),
so this is the only direction left — KV is at its 3-slot floor (5,063 needed of
5,120).

Named prediction, because today's two points say the slab is a THRESHOLD and not
a slope (22,208 -> 3,397 t/s, 24,000 -> 3,290 t/s at 43.5k single-stream): this
arm buys ~1,600 resident expert slots and ~0 prefill. The point that moves
prefill is 26,071 (2026-10-11: 4,379 t/s), fundable only at two slots. Prefill
moving > +-3 % here falsifies the threshold reading.

Seam: the ceiling gate now derives from the engine's budget table (30,969) and
is the single owner of the pair arithmetic; the duplicate I put in the shape
test is removed.

scripts/serve-frank-archon.sh

@@ -15,10 +15,10 @@
 # the P2P answer per pair) — read it after every resize.
 # Deployed shape (2026-10-13): THREE decode slots x 200,000 tokens, fp8
 # (quantized) KV in a 5,120 MiB pool (contract 3 x 200,000 + 1.3 %) and a
-# 24,000 MiB resident expert slab — the pair is the measured 29,120 MiB/card
-# ceiling, spent on the slab because prefill is slab-limited. 44 GiB/rank
-# pinned expert pool, MTP depth 2, prefix cache host 8 GiB + disk 64 GiB, PLE
-# pinned in RAM.
+# 25,600 MiB resident expert slab — 30,720 MiB of the 30,969 MiB the engine's
+# own budget table makes claimable, spent on the slab because prefill is
+# slab-limited. 44 GiB/rank pinned expert pool, MTP depth 2, prefix cache host
+# 8 GiB + disk 64 GiB, PLE pinned in RAM.
 #
 # The root unit (scripts/frank-archon.service, User=dank,
 # LimitMEMLOCK=infinity) grants the pin budget: 2 x 44 GiB expert pools +