v0.26.0

Process Modeler design rebuild

• Rebuild the Process Modeler around the pinned Riptide Diagram reference:
  design-sized cards, gateways, events, frames and notes; rounded orthogonal
  routing, pinned endpoints, line controls, drag previews and a 16px grid.
• Add a grouped searchable palette, business and technical views, host-supplied
  run metrics, nested outline, checks, variables, connections and shortcuts,
  plus a controlled field inspector with action and expression inputs.
• Strengthen host-authoritative validation and read-back: a readable projection
  is emitted only after validation succeeds. Riptide remains responsible for
  workflow conversion, persistence and save policy.
• Add responsive palette/details drawers, multi-selection and arrangement,
  keyboard navigation and focus restoration, accessible announcements and
  reduced-motion handling. Update Storybook examples, documentation and tests.
• React, Angular, Vue and Svelte adapters ship at 0.26.0 in lockstep.