docs(physics): record cutover slice C3c completion + closeout

C3c COMPLETE at 529e0e9d in the placement-cutover plan (five fix slices,
R1 dual-review round, final gates). New closeout research note. ISSUES
#276 (settle-CellId discard), #277 (route-1 far-Create radius bound),
#278 (user-session triage bundle). Register AD-60/AD-61 numeric order.

The next slice before C5 is the 6b28ff99 O(changed) collision clone
(soak convergence); C4 resumes after.

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

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

@@ -162,11 +162,37 @@ same commit) → docs/handoff commit. No workarounds; no fused slices.
     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
-    (harnesses: `tools/run-connected-world-lifecycle-gate.ps1`,
-    `tools/run-connected-r6-soak.ps1`).
+  - **C3c — the host flips (production) — COMPLETE at `529e0e9d`
+    (2026-08-02, dual Opus reviews: initial FAIL 2+2 MAJOR → R1 fix
+    round → delta PASS both).** Both hosts register initial Creates
+    through residence + conductors via the shared
+    `RuntimeFirstEntryDriveController`; Controller setter sealed;
+    rebucketing presentation-only strictly while the residence is
+    ACTIVE (post-residence entities take the full legacy path including
+    the `prepare_to_enter_world` clock edges); content-less headless
+    keeps pre-flip direct registration. Five fix slices landed inside
+    the cutover, each connected-gated: F1 (Runtime ownership seam for
+    movement stats/server physics — the post-logout retired-controller
+    crash), F2 (the login activation wedge: admission-prefix gate
+    factored from the seal, rearm generation identity, auto-entry
+    requires the published controller), F3 (landblock-prefix 0-sentinel
+    → explicit absent-id; corner landblocks legal), F4 (diagnosis only:
+    the nine-stop soak's convergence failure is pre-existing `6b28ff99`
+    whole-world collision-clone throughput — its fix is the next slice
+    before C5), F5 (local-player first-entry ground contact via the
+    shared `SpawnPlacementSettler` at `FinalizeActivation`; the
+    standing-cast airborne rejections are gone; register AD-61). R1
+    additionally armed the login constraint leash at the committed
+    placement (`HandleReceivedPosition` 0x00453FD0 analog) and
+    refreshed AD-42. Final gates: complete solution 10,816/0/4 skips;
+    lifecycle/reconnect gate PASS (`connected-world-gate-20260802-
+    175401`). Closeout:
+    [`2026-08-02-c3c-cutover-closeout.md`](../research/2026-08-02-c3c-cutover-closeout.md).
+    **Carried to C4/C5:** route-1 far-Create service-window conversion
+    if either streaming/broadcast radius changes (#276); the
+    window-departure park narrowing; `NotifyRetirement`-on-active-entry
+    subscriber invariant; the reachable equip-mid-conductor fail-fast;
+    settle-CellId discard (#276-adjacent, see ISSUES).
 - **C4 — remaining routes: 2 (ForcePosition), 3 (portal, with the
   `RuntimeWorldTransitState` → `RuntimePortalPlacementAuthority` adapter),
   4 (remote Create/Position; delete `RemoteTeleportController`/`Placement`