docs(physics): record cutover slice C3b completion

C3b landed at 0934a121 with dual review PASS. The plan records the
remote-entry mechanism and its verified retail anchors; the float-gates
doc gains the port note pinning the NaN dispositions (friction's
sanctioned skip; elasticity and translucency routed exactly as the
binary; ACE's elasticity NaN divergence recorded). Every dormant C3
prerequisite is now complete — C3c, the host flip with the connected
gates, is the sole remaining piece of C3.

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

docs/plans/2026-08-02-placement-cutover.md

@@ -151,9 +151,17 @@ same commit) → docs/handoff commit. No workarounds; no fused slices.
     activation commit onward (abandonment leaves it to ordinary entity
     teardown — retail has no entry-flow rollback); EvaluateActivation's
     post-commit DeferredCell overload is encapsulated behind Advance.
-  - **C3b — remote body construction at Create (dormant):**
-    retail-anchored body construction from the wire PhysicsSpawnData per
-    `set_description` order for residence-route remote/creature Creates.
+  - **C3b — remote body construction at Create — COMPLETE at `0934a121`
+    (2026-08-02, dual reviews PASS).** `RuntimeRemoteBodyDescription` +
+    `RuntimeRemoteFirstEntryState`: the full `set_description` order with
+    the byte-certain gates (friction [0,1] inclusive, NaN sanctioned-skip;
+    elasticity clamp with retail's unordered-to-zero; translucency
+    != 0.0f), the movement-branch discriminator on retail's
+    `movement_buffer != 0` (empty-buffer → placement branch, no autonomy),
+    motion-table zero-id pass, ctor-defaults for absent wire fields, and
+    never-clobber coexistence with the build-at-first-motion production
+    path. The acknowledge discriminator is one shared body
+    (`RuntimeFirstEntryAcknowledgement`) for both conductors. Dormant.
   - **C3c — the host flips (production):** both hosts onto the complete
     machinery; seal the Controller setter; presentation-only
     rebucketing; the connected lifecycle/reconnect + nine-stop gates

docs/research/2026-08-02-set-description-float-gates.md

@@ -219,3 +219,13 @@ false"), which is a documented quirk of this exact MSVC x87 codegen
 pattern and not something the retail struct's `float` fields would
 ever hit in practice (friction/translucency are authored data, never
 NaN).
+
+## Port note (C3b, `RuntimeRemoteBodyDescription.cs`)
+
+acdream's friction port uses `f >= 0.0f && f <= 1.0f`, which deliberately
+SKIPS NaN rather than reproducing the unordered-goes-to-apply codegen quirk
+tabled above — the sanctioned modern-boundary deviation this doc
+pre-declared. Elasticity's setter port (`!(e >= 0f)` first arm) and
+translucency's `!= 0.0f` gate both route NaN exactly as the binary does
+(0f and apply respectively); ACE's `set_elasticity` sends NaN to 0.1f and
+is divergent from the binary on that edge.