CZ leakage amplification calibration nodes (33a / 33b)

[Deepakkhurrana]

Summary

Adds two CZ coupler-amplitude calibration nodes that tune coupler_flux_pulse.amplitude by sweeping amplitude against repeated CZ cycles and selecting the value that best preserves |11⟩.

Why

CZ calibration on tunable-coupler pairs needs a dedicated step to tune coupler_flux_pulse.amplitude so repeated CZ gates preserve |11⟩ instead of leaking population out of the computational subspace. Until now, the CZ chain jumped from conditional-phase nodes (32a/32b) straight to virtual-Z phase compensation (33), with no node targeting coupler amplitude via leakage / |11⟩ preservation.

What

Introduces shared calibration_utils/cz_leakage_amp for analysis, plotting, and parameters. Renames the existing phase-compensation node to 34 so leakage calibration occupies 33.

• 33a — Standard leakage error amplification: prepare |11⟩, repeat CZ for n = 1…N, measure P(11).
• 33b — PALEA protocol (Marxer et al., arXiv:2508.16437): after each CZ, undo virtual-Z phases, apply DD (EF π on high-frequency / leakage qubit, g–e π on low-frequency qubit), restore phases; sweep even n = 2, 4, ….
  Both nodes share the same dataset schema, analysis pipeline, and plots.

Shared utilities (calibration_utils/cz_leakage_amp)

• parameters.py — Amp sweep, number_of_operations, GEF readout flag
• analysis.py — process_raw_dataset (amp_full coord), fit_raw_data, FitResults
• plotting.py — P(11) heatmaps and mean P(11) vs coupler flux with optimal-amplitude markers on the pair grid
  Uses QubitRoles and verify_moving_qubit (with repair_routing=True) for flux-pulse routing consistency.

PALEA-specific (33b)

• Precomputes cz_phase_shifts_map: maps phase_shift_control / phase_shift_target onto high/low qubits by frequency (without assuming control = high).
• Undoes and reapplies CZ virtual-Z around the DD layer so PALEA sits in a phase-neutral sandwich.

Nodes reorganization

• 33_cz_phase_compensation.py → 34_cz_phase_compensation.py (leakage calibration inserted before phase compensation).
• Graph 99 and README.md updated

[paulQM]

LGTM

[HuanQM]

Small comments on unused code.

[Deepakkhurrana]

@HuanQM the requested changes have been addressed.