v1.2.2

Eulerian upgrades, unified ParaView writers, and CI-based PyPI deploy. Also live on PyPI as flowtracks 1.2.2.

Eulerian (Lagrangian → Eulerian)

• Sub-threshold voxels now NaN (never fake zero velocity) + new boolean valid mask; legacy zero-fill still available via fill_value=0.0
• Opt-in pre-binning QC gates (finite + speed range) and finite_difference_velocity helper
• chunk_frames: memory-bounded chunked accumulation, bit-identical to the single pass
• New eulerian_windowed: sliding-window means for non-periodic flows (searchsorted slices)
• derived_fields: upfront NaN/Inf cleaning, counts + fluid_min masking, PRT counts mode, matlab/physical gradient convention

Writers / pipeline

• Unified pyvista writers (.vtp/.vti/.vtr/.pvd), Zarr demo dataset, provenance tracking, vortex + wall-shear analysis, vectorized stitching; vtk/tables now optional

CI / deploy

• PyPI publish via Trusted Publishing (OIDC) from OpenPTV/postptv tags; no API-token secret needed

Full test suite green on 3.11/3.12/3.13.