Emit `expanded`/`collapsed` end-state events only for expandable components

[Elijbet]

Check existing issues

• I have checked for existing issues to avoid duplicates

Description

Emit only end-state expanded/collapsed events for expandable components pending animation architecture decisions.

• We are awaiting final decisions from the Animation Effort regarding whether/how expandable components will support transitions and animations.
• As an interim solution for all expandable components, emit only end-state events immediately on state change.
• Do not emit start events (beforeExpanded/beforeCollapsed) or tie event timing to transitions/animations until requirements are finalized.
• This approach unblocks engineering, provides a consistent event API for consumers, and avoids premature abstraction or excessive duplicate work if transition requirements change.
• Once animation requirements are clear, we will:
  • Add start events as appropriate.
  • Wire up transition/animation utilities to ensure event timing matches visual state.
  • Refactor as needed to align with the finalized architecture.

Acceptance Criteria

Directly emits expanded/collapsed end-state events only for expandable components.

Relevant Info

Falls under #6473

Which Component

action-bar
action-group
action-menu
action-pad
panel
accordion-item - #4531
block
block-section
list-item
tree-item - #8945

Example Use Case

No response

Priority impact

impact - p3 - not time sensitive

Calcite package

• @esri/calcite-components
• @esri/calcite-components-react
• @esri/calcite-design-tokens
• @esri/calcite-ui-icons
• @esri/eslint-plugin-calcite-components

Esri team

Calcite (dev)