feat(colormap): add ColorMapRegistry service and wire to chart panel

[pabloinigoblasco]

Summary

Introduce a dedicated ColorMapRegistry as a session-wide service — peer to DataEngine — that stores plugin-registered color evaluation callbacks and exposes an active selection to rendering consumers.

Plugins that publish colormaps receive the registry through a new optional bind_colormap_registry entry on the toolbox plugin vtable. The data-plane toolbox host no longer carries colormap-specific callbacks.

Why

The previous shape placed register_colormap / unregister_colormap on the toolbox host vtable. That coupled the generic data/writing host to a presentation concern and left no first-class home for the registry state. Lifting the registry to its own service — independent class, its own ABI fat pointer, owned by MainWindow alongside DataEngine — keeps each side cohesive: the host handles data, the registry handles named colormaps, and the chart reads from the registry directly.

Key pieces

• pj_datastore/colormap_registry.{hpp,cpp} — new class with registerMap / unregisterMap / setActive / evaluate / hasActive. Qt-free, header + cpp.
• pj_datastore/colormap_registry_host.{hpp,cpp} — makeColorMapRegistryHost(ColorMapRegistry&) adapter that exposes a registry reference as a PJ_colormap_registry_t ABI fat pointer.
• pj_base/plugin_data_api.h — drop register_colormap / unregister_colormap from PJ_toolbox_host_vtable_t; add the new ABI types.
• pj_base/toolbox_protocol.h — add optional bind_colormap_registry to the toolbox plugin vtable.
• pj_base/sdk/plugin_data_api.hpp — drop registerColorMap / unregisterColorMap from ToolboxHostView; add ColorMapRegistryView C++ wrapper.
• pj_base/sdk/toolbox_plugin_base.hpp — bindColorMapRegistry virtual, trampoline, colorMapRegistry() accessor.
• pj_plugins/toolbox_handle.hpp — bindColorMapRegistry pass-through.
• pj_proto_app — owns the single ColorMapRegistry, threads it into each ToolboxSession, and feeds a live view to ChartPanel via setColorMap. Chart now tracks the last value per series.
• Tests — mock vtables in pj_plugins updated.

Breaking change

This changes the toolbox host ABI. The matching plugin-side migration is in pj-official-plugins#NN (feat/colormap-registry-migration) — they must be merged together for CPM-pulled builds to stay green.

Test plan

• pj_base + pj_datastore + pj_plugins tests green (ctest -R "toolbox_plugin_test|quaternion" passes)
• Full build including proto_app + 12 plugins compiles with -Wall -Wextra -Werror
• Runtime: open proto_app, load data, open ColorMap Editor, define a map, apply, see chart colors update