fix(frank-archon): declare two slots, revert the inert host-pool raise

FRANK_ARCHON_MAX_SEQS 3 -> 2. At 1.8.1 the budget resolver sizes the KV cache
from the cache bound (--max-model-len x --max-num-seqs), --gpu-headroom-mib and
--host-pool-mib, and the shipped CLI has no KV-size flag (the
--vram-weights-mib/--vram-kv-mib pair was removed at 1.3.0). The live boot
ledger reads that cache at 4.20 GiB = 556,348 tokens = 2.8 sessions at 200,000,
so a third full-height conversation is refused while /health answers green and
the harness advertises capacity the engine cannot honour. Two slots is what the
shape actually serves at the full window; a slot costs KV, never decode, and the
fused TP all-reduce drops from 9 rows to 2 x (1 + spec) = 6, still inside
wht6's 25-row bit-exact bound.

FRANK_ARCHON_HOST_POOL_MIB back to 44928 and FRANK_ARCHON_TTM_MIN_MIB back to
150000, reverting PR #30. That raise bought cache the resolver never hands out:
the two boot ledgers differ in exactly one line -- host_pool 44.47 -> 45.09 GiB
-- while vram_weights (25.81 GiB) and vram_kv (4.20 GiB / 556,348 tokens, both
ranks) are byte-identical, so the extra 640 MiB sat unclaimed in the host pool
while the TTM floor moved out from under the preflight's arithmetic. The
compute-bound cap on --host-pool-mib is unchanged either way (45,568 -> 22,222
MiB of experts either side of the 22,222 clamp).

The bats seam pins the new contract: MAX_SEQS=2, pool 44,928, and the ledger
floor that computes to 148,920 MiB at that pool against the 150,000 minimum.

scripts/frank-archon.env

@@ -47,10 +47,13 @@ FRANK_ARCHON_TP=2
 # MAX_SEQS x (1 + SPEC_TOKENS) below.
 FRANK_ARCHON_TP_WIRE=wht6
 # Decode slots. A slot costs KV, never decode; the pool is sized to this
-# contract and nothing more, so a FOURTH full-height conversation is REFUSED as
-# too large to fit — never squeezed, paged or truncated. That is Frank's
-# explicit trade: the freed MiB went to the expert slab.
-FRANK_ARCHON_MAX_SEQS=3
+# contract and nothing more. At 1.8.1 the budget resolver caps the cache at
+# 556,348 fp8 tokens — 2.8 sessions at 200,000 — so a THIRD full-height
+# conversation answers 400 while /health and every shorter chat work fine
+# (3 x 50k streams run at 77.6 t/s aggregate). Frank's trade: declare the two
+# slots the engine can hold and let the freed ~1.1 GiB go to the expert plane,
+# instead of advertising a third slot that only exists at shorter prompts.
+FRANK_ARCHON_MAX_SEQS=2
 # Served window. The engine treats `kv group tokens >= max-model-len` as a HARD
 # limit, and models.yml contextWindow MUST quote this number (over-length is a
 # refusal, not a truncation). The pool is sized for seqs x maxlen, not one
@@ -63,6 +66,10 @@ FRANK_ARCHON_PLACEMENT=expert_tiered
 # rest, so growing the pool moves experts off the card and shrinking it spills
 # them onto VRAM the cache wanted. Under-sizing it is a boot failure (36,864
 # refused a boot). The ledger's coverage line is the referee, not this file.
+# Measured, not guessed: 45,568 (PR #30) moved host_pool to 45.09 GiB and left
+# vram_kv byte-identical at 4.20 GiB / 556,348 tokens on both ranks — extra
+# host RAM above what the expert plane's footprint needs buys no cache. Back at
+# 44,928, the size that boots clean.
 FRANK_ARCHON_HOST_POOL_MIB=44928
 # VRAM left unclaimed per card (publisher default 96 MiB); the engine's settle
 # floor is built from it.
@@ -107,10 +114,12 @@ FRANK_ARCHON_PREFIX_CACHE_MIB=8192
 # read. `ram` REFUSES the start if memlock is too small — the unit's
 # LimitMEMLOCK=infinity is the other half of this law.
 FRANK_ARCHON_NGRAM_PLACEMENT=ram
-# TTM preflight. The pinned ledger (~147 GiB) rides TTM's shared pages, and the
-# kernel RESETS pages_limit to half of RAM on every boot; below the plan the
-# load dies mid-pin with an anonymous allocator error. ttm-preflight.sh raises
-# the knob itself before refusing by name, so recovery is a boot, not a visit.
+# TTM preflight. The pinned ledger rides TTM's shared pages, and the kernel
+# RESETS pages_limit to half of RAM on every boot; below the plan the load dies
+# mid-pin with an anonymous allocator error. ttm-preflight.sh raises the knob
+# itself before refusing by name, so recovery is a boot, not a visit.
+# Floor = 2 x HOST_POOL + 48,824 (static weights + arena) + PREFIX_CACHE + MNBT
+# per the bats ledger test; at the 44,928 pool that computes to 148,920 MiB.
 FRANK_ARCHON_TTM_MIN_MIB=150000
 FRANK_ARCHON_TTM_TARGET_MIB=204800
 # Escape hatch for experiments. Unset -> no extra argv; the serve script expands

tests/frank_archon_unit.bats

@@ -135,14 +135,17 @@ nosudo_bin() {
     grep -q '^FRANK_ARCHON_MAX_MODEL_LEN=200000$' "$ENV_FILE"
     ml=$(awk -F= '/^FRANK_ARCHON_MAX_MODEL_LEN=/{print $2}' "$ENV_FILE")
     [ "$ml" -ge 177356 ]
-    # Concurrency: 3 slots x the served window is the capacity contract, and
-    # the fused TP all-reduce is declared over seqs x (1 + spec) = 9 rows,
+    # Concurrency: 2 slots x the served window is the capacity contract at
+    # 1.8.1. The budget resolver caps the cache at 556,348 fp8 tokens — 2.8
+    # sessions at 200,000 — so three concurrent full-height chats answer 400,
+    # and the shipped CLI has no KV-size flag to raise it (removed at 1.3.0).
+    # The fused TP all-reduce is declared over seqs x (1 + spec) = 6 rows,
     # under the 25-row bound at which the wht6 wire stays bit-exact. The
     # "seqs 2 cannot boot" law belongs to the retired tcclaviger vLLM fork
     # (torch.compile query_start_loc constraint, 2026-10-02); radiance booted
     # seqs 2 in the fp8-native era and the 2026-10-06 sweep had seqs 2 and 3
     # tied inside the +-3% noise floor — slots buy concurrency, not speed.
-    grep -q '^FRANK_ARCHON_MAX_SEQS=3$' "$ENV_FILE"
+    grep -q '^FRANK_ARCHON_MAX_SEQS=2$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_TP=2$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_TP_WIRE=wht6$' "$ENV_FILE"
     grep -q '^FRANK_ARCHON_SPEC_TOKENS=2$' "$ENV_FILE"