Qiskit / qiskit-addon-slc / 37621171072

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feat: animate shaded lightcones on a QPU coupling map (#65)

Adds `animate_shaded_lightcone`, which projects the 1- and 2-weight bounds onto
a QPU's coupling map and animates them box by box. The existing
`draw_shaded_lightcone` becomes hard to read for circuits acting on qubits whose
connectivity is higher than a 1D line.

The two helpers taken from `qiskit_ibm_runtime.visualization.utils` are vendored
rather than imported: that is a private module of a package which is not a
runtime dependency.

The qubit layout picks its strategy from the coupling map's maximum
connectivity, rather than from the qubit numbering as before: a path is laid out
along a single row, a ring folds into a rectangle, a square lattice is placed
directly by walking its axes, and a heavy-hex lattice has its rows pre-placed as
straight lines so that only the rungs between them need searching for.

Not every coupling map has a grid placement, and the ones that do not now say so
instead of failing obscurely. A grid is bipartite, so it contains no odd cycle
and no odd ring can be drawn; a 6-ring is even but equally impossible, since its
only placement puts two uncoupled qubits side by side and would imply a coupling
the device does not have. Rings of 4, or of 8 or more even qubits, are fine.

Closes #47.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

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