2062013 - Implement availability selector UI

Status: NEW

(Calendar :: Calendar Frontend, enhancement)

Description

[Alex Schmitz]

Summary:

Implement the sticky-footer availability selector as a draft-only control.

Links:

• Zeplin sticky footer/availability/privacy annotations: https://app.zeplin.io/project/66dd0f2b2fe8f1b63cda36f1/screen/6a0f2f285393a283202254bc

• Interaction guide: Create > Availability/privacy: https://docs.google.com/document/d/15OpMthOHmBGyPpDBNRW8vp6uCxeoitBp8n7Fti3LD10/edit?tab=t.why4m6lqup0#heading=h.5fg39gqf1jkr

• Planning: Select Menu - Suggested Implementation Slices

• Planning: Questions - Q16 Additional Availability And Privacy Values
  Acceptance criteria:

• The availability selector provides Default, Busy, and Free options. Any additional existing Thunderbird availability values require product confirmation before they are exposed.

• The selector renders the current session’s plain availability draft through stable storeObserver selections. Do not use getters that pull state from the store.

• Availability state is a plain enum value only; it contains no calIEvent, calendar object, preference value, DOM node, or open-popup state.

• Selecting an option dispatches one narrow availability-section patch and changes draft state only.

• Popup visibility, active option, keyboard navigation, and focus restoration remain local selector state.

• A route/session replacement closes stale popup interaction and prevents an obsolete selection event from patching the newer draft.

• The selector uses the sticky footer’s established layout and does not grow, resize, or re-anchor the dialog or call PositionedDialog.

• Availability loading, create defaults, and event-property persistence remain outside this story and belong to Bug 2062016.

• Add focused tests for the allowed options, draft-only selection patches, inaccessible-until-confirmed additional values, keyboard and accessible naming behavior, stale-session protection, footer layout integration, and axe coverage where supported.

Out of scope:

• Availability loading, default selection, preference reads or writes, calendar-property conversion, Save-time persistence, a generic dropdown service, and direct calendar mutation.