Generalize synchronized remap to multiple pinned body rectangles

docs/synchronized_leaf_remap.md

@@ -113,22 +113,24 @@ 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
+also accepts stationary Circles in separated L2 rectangles. Every body’s
+**complete containing rectangle must remain identical**. Several bodies may
+share one pinned rectangle; there need not be any fluid-only rectangles.
+Separated fluid-only rectangles may be added, removed or moved. 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.
+Supply all original root edge-frame definitions in their construction order.
+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,
+compares exact ordered circle centers/radii, 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.
+rectangle fail without device reads or allocations; reordered bodies fail
+too. 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
@@ -139,12 +141,20 @@ boundary and velocities must match exactly.
 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.
+old fluid children. The helper checks the old/new body pins and boundary too.
+Its immutable `pinned_rectangles` is a canonical, deduplicated tuple, empty for body-free layouts; rectangle input
+order does not affect it. Scalar-parent window offsets remain part of the
+coordinate conversion.
 
 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
+Multiple-body CPU coverage: `tests/unit/test_multiple_pinned_remap.py`.
+`tests/validation/multigrid/test_multiple_pinned_remap_gpu.py` adds two pins,
+two independently updated Jets, variable fluid-region counts and add/move/remove
+immediate comparisons with CPU transfer. All nine solid-excluded area-weighted
+population integrals, exact overlap and nonleaf NaNs are checked.
+These new 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.