[jencompgeek]

What is in this PR?

Builds out the full pregame (pre-event early access) experience for eventAssistant
conversations. Organizers can configure how many minutes before the scheduled start
participants get early access to the room, a private warm-up question (organizer-written
or AI-generated, open text or single choice), and whether a recap of pregame activity
posts to the group chat once the event starts.

Also closes a gap where a conversation could still
be edited while it was already in its open pre-event window.

Changes in the codebase

• Added the pregame feature to eventAssistant's conversation type
  (src/conversations/eventAssistant.ts): preEventMinutes, warm-up question source
  (organizer-written / AI-generated) and format (open text / single choice) with friendly
  option labels, and whether to post a recap on start.
  — including one nested inside a feature's own config, like pregame.preEventMinutes —
  directly onto the created conversation document instead of only into an agent's
  agentConfig. Renamed the underlying AgentProperty/resolveAgentProperties to
  PropertyBinding/resolvePropertyBindings since it's no longer agent-specific.
• updateConversation now also rejects edits while a conversation is in its open pre-event
  window, not just while fully active, since participants are already engaging in the
  pregame channel by then.
• Fixed the OpenAPI ConfigProperty.type enum, which was missing array even though it's
  a supported type.
• Modified eventAssistant to skip group chat opener when not configured

Documentation and automated testing

Did you:

• document any breaking changes in your commit messages?
• document your changes as comments in the code? Use TSDoc format where appropriate.
• update the README and docs to be clear and easy to use for end users and developers?
• add and/or update automated tests?
• update team documentation of any new or changed environment variables?

No breaking changes and no new environment variables, so those two are n/a.

Testing this PR

Test in conjunction with FE PR berkmancenter/nextspace#240

• Create an eventAssistant conversation with the pregame feature enabled
• Try both warm-up sources (organizer-written vs. AI-generated) and both formats (open
  text vs. single choice); confirm the right prompt/options render in the private chat in the participant view within 1-2 minutes of pregame window opening
• While the conversation is inside its pre-event window, attempt an edit via the API or NS
  and confirm it's rejected with "Cannot update a conversation during its pre-event
  window."

Additional information

The propertyBindings mechanism is general-purpose (not pregame-specific) — it's what lets
any conversation type mirror a resolved feature-config value onto a real top-level field on
the conversation document, which preEventMinutes needed since several scheduling files
(preEventWindow.ts, scheduleConversationTimers.ts) read it directly off the document
rather than digging through conversation.features.