docs(physics): decompose C3 after the flip halted with findings

The first C3 implementation pass landed C3-1 (fe02c4f5) and correctly
stopped on two structural gaps no planning document captured: the local
player's first-entry circularity (the residence opens its placement at
Create, submission needs a body, and only the zero-caller publication
chain can attach one — resolvable by the campaign handoff's own route-1
order, but no driveable state machine exists) and the absence of any
remote-creature body construction at Create time (retail builds physics
in ACCObjectMaint::CreateObject; ours arrive with first motion). The
plan now records the C3a (first-entry conductor, dormant) / C3b
(retail-anchored remote body construction at Create, dormant — its
contract must first resolve set_description's three FPU-elided
friction/translucency gates from the PDB-paired binary) / C3c (the
actual host flips + connected gates) decomposition.

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

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

@@ -114,13 +114,39 @@ same commit) → docs/handoff commit. No workarounds; no fused slices.
   comment-enforced; `IsCurrent(Operation)` remains available and a new
   reentrancy-spanning call site would silently inherit the tautology —
   its doc comment warns.
-- **C3 — spawn-frequency cutover: routes 1 + 8.** Flip graphical AND
-  headless initial Create/login registration to
-  `RegisterEntityWithInitialResidence` + executor + placement receipts
-  together; `MaterializeProjection`/`BuildControllerAndCamera`/
-  `SynchronizeLocalPlayer` become projection + acknowledgement only;
-  presentation-only rebucketing (`RebucketLiveEntity` loses `CommitRebucket`).
-  Gates add the exact lifecycle/reconnect connected route.
+- **C3 — spawn-frequency cutover: routes 1 + 8 — DECOMPOSED 2026-08-02
+  after the first implementation pass stopped with findings.** C3-1 (the
+  public executor-completion surface via
+  `RuntimePlacementProjectionChannel.TryGetInitialCreateCompletion`)
+  landed separately. Two structural gaps halted the flip, both real and
+  neither in the planning docs:
+  **(B)** the local player's residence lease opens its SetPosition
+  operation at Create time, but `SubmitPreparedPlacementCore` requires a
+  pre-existing canonical body that only the zero-caller publication chain
+  can attach — first-entry needs an explicit resumable sequence
+  (begin-placement → publication Prepare/Commit attaches the body →
+  authored-mover submit → Place receipt → Execute), which matches the
+  campaign handoff's route-1 required order but exists nowhere as a
+  driveable state machine;
+  **(C)** ordinary remote-creature Creates classify to `SetPosition` but
+  have NO production body-construction path at Create time (bodies arrive
+  with first motion today; retail constructs physics at CreateObject via
+  `ACCObjectMaint::CreateObject`/`set_description`, which our retail
+  notes fully document — the defaults come from the wire PhysicsDesc,
+  not invention).
+  Sub-slices, each with the standing contract/dual-review/gate
+  discipline:
+  - **C3a — Runtime first-entry sequencing (dormant):** the resumable
+    local-player entry transaction binding residence → publication
+    body-attach → mover submit → receipt → Execute, test-driven.
+  - **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.
+  - **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
+    (harnesses: `tools/run-connected-world-lifecycle-gate.ps1`,
+    `tools/run-connected-r6-soak.ps1`).
 - **C4 — remaining routes: 2 (ForcePosition), 3 (portal, with the
   `RuntimeWorldTransitState` → `RuntimePortalPlacementAuthority` adapter),
   4 (remote Create/Position; delete `RemoteTeleportController`/`Placement`