feat(plot): adopt cleopatra 0.29 and expose ColorBar on the mesh/UGRID plot path

[MAfarrag]

Context

cleopatra 0.29 (serapeum-org/cleopatra#244, closing #239) lifted the typed ColorBar spec to the shared
Glyph base, so MeshGlyph.plot / .animate (and FlowGlyph / KDEGlyph / ScatterGlyph / PolygonGlyph /
VectorGlyph) now accept colorbar=bool | ColorBar | None and emit the loose-cbar_* DeprecationWarning
uniformly. pyramids pins the [viz] floor at cleopatra >= 0.28, where MeshGlyph.plot's colorbar is still a
plain bool with no ColorBar support.

This is the mesh half of the typed plot-spec migration. The raster half is done — #926 (adopt 0.28 + the
typed specs) and the refactor/plot-deprecate-loose-cbar-kwargs branch (surface the cbar_* deprecation on
every raster plot path). The UGRID example notebooks are the only remaining first-class cbar_label users
because the mesh backend could not take a ColorBar — which cleopatra 0.29 now fixes.

Related: #926, and cleopatra #239 / #244.

Problem / Current Behaviour

• UgridDataset.plot / mesh_render cannot forward colorbar=ColorBar(...) — on the 0.28 floor MeshGlyph.plot
  has colorbar: bool, so the typed spec would be rejected.
• The UGRID example notebooks (docs/examples/netcdf/ugrid/*.ipynb) still configure the colour bar with the
  loose cbar_label because there was no typed alternative on the mesh path.
• Loose cbar_* on the mesh path never warned (cleopatra 0.28 added the deprecation only to ArrayGlyph); 0.29
  adds it to MeshGlyph, so once adopted the mesh path warns like the raster path.

Affected locations

File	Symbol	Notes
pyproject.toml	[project.optional-dependencies] viz	bump floor to cleopatra[tiles]>=0.29.0
src/pyramids/dataset/_plot_helpers.py	mesh_render	forward colorbar= (bool | ColorBar) to MeshGlyph.plot
src/pyramids/netcdf/ugrid/plot.py	plot_mesh_data	accept + pass colorbar=
src/pyramids/netcdf/ugrid/dataset.py	UgridDataset.plot	expose/document colorbar=
docs/examples/netcdf/ugrid/*.ipynb	—	migrate cbar_label → colorbar=ColorBar(label=...)

Proposed Solution

• Bump the viz extra to cleopatra[tiles]>=0.29.0 (regenerate pixi.lock).
• Forward colorbar= (bool | ColorBar) through mesh_render → plot_mesh_data → MeshGlyph.plot, mirroring
  the raster facade, and document it on UgridDataset.plot (re-using pyramids.plot.ColorBar).
• Migrate the UGRID example notebooks from cbar_label onto colorbar=ColorBar(label=...).

Out of Scope

The raster cbar_* deprecation surfacing (done on refactor/plot-deprecate-loose-cbar-kwargs).

Effort Estimate

Size: M — Rationale: a dep bump + mesh-facade forwarding + notebook migration; no new algorithm.

Definition of Done

• viz floor is cleopatra[tiles]>=0.29.0; pixi.lock regenerated
• UgridDataset.plot(colorbar=ColorBar(...)) renders on the mesh path
• the UGRID example notebooks use colorbar=ColorBar(...) (no loose cbar_label)
• tests cover the mesh colorbar= forwarding; existing tests pass