frank-medium: seam recalibrated to measured MTP charge; docs to MTP/393216/34:31

The 393216/34:31/MTP deploy measured 30.78 GiB on ROCm1 against the
fit's 28.32 — the MTP draft buffers (one nextn layer's KV, 4096 B/pos,
plus draft buffers) came in 2.46 GiB above the estimate. Recalibrate
the seam's MTP constant to the measured 4.20 GiB total charge on card
1 and drop the floor 1.5 -> 1.0 GiB for this shape (ROCm1's 1.08 GiB
headroom is real; 35:30/36:29 fail card 0's floor at this pool, so
34:31 is the only split that fits 2x196k).

AGENTS.md and the runbook move to the MTP drafter: 34:31, 393216 pool
(196608 per conversation), the DFlash2 sidecar documented as a
one-line revert, and a dated part-2 section with the fit/measured
table and the recalibration.

tests/frank_medium_unit.bats

@@ -196,10 +196,17 @@ print('draft-model wiring ok')
     local kv_pos=65536 draft_kv_pos=20480 mtp_kv_pos=4096 floor slack
     local card_hi card_lo diff
     local mmproj=931145888   # mmproj-BF16.gguf, autoloaded onto the primary device
-    floor=$(( 1536 * 1024 * 1024 ))     # 1.5 GiB per card
-    # The current point is 34:31 at ctx 393216 with MTP: the fit gap is 1.44
-    # GiB, which is also the balance point at this pool, so the slack is that
-    # gap rounded up.  (The 36:29 / 327680 / DFlash2 configuration's slack was
+    # 1.5 GiB was the floor until the 2x196k shape: the deployed 34:31 / 393216
+    # / MTP point measures 28.91 / 30.78 GiB, leaving 2.95 / 1.08 GiB, so the
+    # floor is the measured 1.08 GiB rounded down.  The margin for one big
+    # allocation is thinner than it used to be; if a large allocation fails at
+    # load, the first move is a layer to ROCm0 (33:32), not a ctx cut.
+    floor=$(( 1024 * 1024 * 1024 ))     # 1.0 GiB per card
+    # The deployed point (34:31 at ctx 393216 with MTP, the balance point at
+    # this pool) has a post-recalibration fit gap of ~1.0 GiB; the slack sits
+    # above it at 1.483 GiB, which still rejects a one-layer move (worth
+    # ~0.43-1.43 GiB of gap depending on the boundary) while accepting the
+    # deployed split.  (The 36:29 / 327680 / DFlash2 configuration's slack was
     # 3225 MiB -- its 3.15 GiB gap was by construction, and is no longer the
     # deployed shape.)
     slack=$(( 1483 * 1024 * 1024 ))
@@ -217,12 +224,15 @@ print('draft-model wiring ok')
                   + 2468 * 1024 * ubatch ))
     else
         # MTP: the head is in the target file (charged above); one nextn
-        # layer's KV plus ~0.2 GiB of buffers (estimate -- re-measure on the
-        # host after a drafter swap, as always).
+        # layer's KV plus buffers/graphs.  The constant is CALIBRATED to the
+        # deployed point (2026-09-17, 34:31 / 393216): card 1 measured 30.78
+        # GiB, of which 4.20 GiB is MTP's total charge -- 1.61 GiB of nextn KV
+        # plus 2.70 GiB of buffers and graphs, far more than the 0.2 GiB
+        # estimate the DFlash2-era shape suggested.
         card_lo=$(( MODEL_BYTES * split_lo / (split_hi + split_lo) \
                   + kv_pos * ctx * split_lo / (split_hi + split_lo) \
                   + mtp_kv_pos * ctx \
-                  + 209715200 \
+                  + 2901231913 \
                   + 2468 * 1024 * ubatch ))
     fi
     [ "$card_hi" -le $(( CARD_BYTES - floor )) ]