Add bounded pinned-circle manual L2 remapping

docs/synchronized_leaf_remap.md

@@ -109,3 +109,42 @@ finite leaves, exact masks and absolute counts. They were not run on the CPU
 host. The separate independent FP64 capture/replay gate is max population
 error **3e-6**, with exact masks; remap mass/momentum allow FP32 roundoff.
 Per-population conservation is not an advancement target under collision.
+
+### Bounded pinned-body extension
+
+`replacement = current.remap_child(rectangles, child_objects=original_objects)`
+now also accepts exactly one stationary Circle in one of exactly two L2
+rectangles. Its **complete containing rectangle must remain identical**;
+only the separated fluid rectangle may change. Existing nesting, four-cell
+gap, full-circle containment, reverse cut-link coverage and two-hop BFL
+transfer-footprint checks still apply. This is manual remapping, not adaptive
+body tracking or runtime body editing.
+
+Supply the original root edge-frame definition used at construction. Do not
+pass `current.child_boundary.objects`: those are projected fine-local copies.
+There is no retained mutable original-object registry. Before reading device
+state, remapping reprojects the supplied definition onto the old topology and
+compares flags, physical cut links, body IDs, q, lever arms, hits, BFL support,
+legacy SurfaceActuation specification and current per-link velocity against
+the existing boundary. Omission, changed geometry/actuation and changed body
+rectangle fail without device reads or allocations. Root object IDs are still
+assigned by list position, as in the constructor.
+
+Jets are taken from the live L2 boundary, including the most recent successful
+`set_jet_amplitude(..., level=2)`. There is no replacement-Jets argument or
+constructor-time Jet snapshot. New blocked addresses may differ; the physical
+boundary and velocities must match exactly.
+
+`RemapTopology.from_config(..., child_objects=..., child_jets=...)` prepares a
+typed `FineBoundary2D`; it derives L2 fluid leaves as ACTIVE minus SOLID. No
+caller mask is accepted. Solids, ghosts and holes are never donors and remain
+NaN, physical-fluid overlap is exact, and exposed L1 still restricts all four
+old fluid children. The helper checks the old/new body pin and boundary too.
+
+Focused CPU mocks: `tests/unit/test_pinned_body_remap.py`. GPU declarations:
+`tests/validation/multigrid/test_pinned_body_remap_gpu.py`, covering no-op
+next-step bitwise identity, moved-fluid A→B→A, current-amplitude preservation,
+physical boundary/velocity equality, source independence and absolute counts.
+These GPU cases have **not been run here**. They do not establish evolution
+accuracy. A 3e-6 FP32-vs-FP64 evolution gate requires a separate independent
+BFL reference; the body-free replay gate above does not establish that claim.