feat: add externalNavigate and refresh actions, restructure action handlers

[fedepini]

Summary

• externalNavigate action: opens an external URL in the browser, with optional target and JQ support on url for dynamic links built from row/widget payload
• refresh action: invalidates TanStack Query cache entries — scoped by resourcesRefsIds, by widgetKinds, or globally when neither is specified
• Action handler refactor: split the monolithic useHandleActions into individual handler files under src/hooks/actionHandlers/ (navigate, openDrawer, openModal, rest, externalNavigate, refresh)
• Schema updates: both actions added to Button, Panel, Table, and Form JSON schemas
• Examples: Button, Panel, and Table example YAMLs extended with cases for both new actions; Table.menu.yaml restructured with a TabList (Examples / Actions tabs) matching the Button and Panel pattern
• Docs: new docs/actions.md covering all six action types with property tables and examples; docs/docs.md updated to reference it; docs/widgets-api-reference.md extended with externalNavigate and refresh property rows

Test plan

• Click a button with externalNavigate (static URL) — new tab opens at the correct URL
• Click a table row action with externalNavigate using a JQ url — URL resolves correctly from row data
• externalNavigate with requireConfirmation: true — confirm dialog appears; cancel aborts navigation
• refresh with no scope — all widgets on the page re-fetch
• refresh with resourcesRefsIds — only the listed widgets re-fetch
• refresh with widgetKinds — all widgets of the listed kind(s) re-fetch
• Table examples page shows two tabs: "Examples" and "Actions"
• Lint passes: npm run lint

🤖 Generated with Claude Code