v1.7.0

New modules

• flowtracks.clean: cleaning chain for raw tracker output -- repair, Savitzky-Golay smoothing, kink split, two stitching passes -- from flat arrays (clean_trajectories), with CLEAN_DEFAULTS (no default frame rate), resolve_settings (defaults <- parameter section <- overrides, with the source of every value), trajectories_from_arrays, kink_split.
• flowtracks.merge: merging the trajectories of two camera systems that see a common volume -- rigid map from same-frame particles (estimate_rigid_map), apply_rigid, overlap_counts, best_partners, duplicates.

Graphics

• animate_trajectories_3d: off-screen 3D movie of trailing beads coloured by a velocity component, with grey back walls, grid labels, custom font and closed outlines (e.g. the rims of a cell).
• Units in axis titles, colour bars and VTK field data.

Other

• Phasing: one shared bin definition (n_frames_in_period, n_phases, phase_width), eulerian_grid aliases.
• Writers record units attributes.
• Render tests skip cleanly on headless machines.