docs(physics): #347 premise revision — retail may alternate too; ftp:edge ratio is the discriminator

The cliff_slide arms are conformant in ACE, our port, and the bytes
(compare constant at 0x794610 verified 0.0), the round-1 slidn:edge
ratio (538:594) refutes a retail retry storm, and the user's
side-by-side speed observation fits alternation. Round-2 cdb script
now counts find_transitional_position; H-A (identical, retire AD-70)
vs H-B (within-tick yield) resolves on one ratio. The temporary
Scratch347 diagnostic test rides along until #347 closes.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/research/2026-08-08-347-fix-contract.md

@@ -120,3 +120,48 @@ Clean-room complete suite; dual Opus review (conformance byte-check of
 cliff_slide's fchs arms + blast radius over every CliffSlide caller);
 retire AD-70 in the same commit; user slope feel gate (~2 min: glide speed
 now matches retail side-by-side; downhill/uphill/hover unchanged).
+
+## PREMISE REVISION (2026-08-08, same session — before any code change)
+
+Three findings force the "retail = full-rate within-tick" premise back to
+OPEN:
+
+1. **cliff_slide's arms are conformant in all three sources.** ACE
+   (`Transition.cs:242-266`), our port, and the byte decode agree on the
+   crease vector, the sign arms, and the compare-vs-0.0 (double at
+   0x794610, verified zero). For the conformance fixture's geometry those
+   arms move the check position INTO the face (the arming tick's probe
+   trace shows primary dist -0.056 -> -0.200 -> -0.487 across the three
+   attempts) — the "dig" is what the code as written does, in retail's
+   bytes too.
+2. **The round-1 counters refute a per-tick retry storm in retail.**
+   slidn:edge = 538:594 ~ 1:1.1. Our alternation shape produces THREE edge
+   entries per sliding-normal set (the dig-retries); retail produces ~ONE.
+   The glide window in the counter progression (edge 0 -> 594 across six
+   1280-vwalk blocks, then frozen) also shows edge growth stopping the
+   moment the hold ended.
+3. **The user's side-by-side observation** ("I cant detect any speed
+   change from retail", #345 gate, 2026-08-08) is consistent with retail
+   ALTERNATING exactly as we do — arm one tick, move the next — and
+   inconsistent with retail moving at double our rate.
+
+Competing hypotheses now:
+- **H-A (retail alternates too):** retail's arming tick runs ONE edge
+  entry (no retry after the cliff-slide Adjusted) and yields nothing; the
+  next tick's pre-projection moves. Then our ONLY divergence is the two
+  extra futile dig-retries per arming tick (invisible — the tick's output
+  is discarded), #347 closes as measured-identical, and AD-70 is RETIRED
+  as a wrong inference, not fixed.
+- **H-B (retail yields within the tick):** the single edge entry precedes
+  a successful same-tick commit. Requires the retried/continued insert to
+  land clean — mechanism unknown given the dig direction — and would keep
+  AD-70 open as written.
+
+**The discriminator is one number in the round-2 capture:**
+`CTransition::find_transitional_position` (~1/tick for the player) vs
+`edge_slide` during the glide window. H-A predicts ftp:edge ~ 2:1
+(edge every other tick); H-B predicts ~ 1:1 (edge every tick). The
+round-2 script (`tools/cdb/345-glide-stacks.cdb`) now counts ftp, prints
+the periodic progression, samples 6 stacks each for edge/cliff/step_down,
+and auto-detaches at 300 edge hits via the fall-through-then-top-level-qd
+recipe. NO code changes until this capture runs.