SCAL-336941 add UpdateTheme host event

[harshitbhardwaj-ts]

Summary

Adds HostEvent.UpdateTheme, which switches an open embed between dark appearance and its default appearance without reloading it. Follows the isDarkMode option from #672.

await embed.trigger(HostEvent.UpdateTheme, { isDarkMode: true });

Changes

• HostEvent.UpdateTheme (wire value 'UpdateTheme') with payload
  UpdateThemeRequest { isDarkMode: boolean }. It is typed in
  HostEventRequestMap, exported from the package and the React entry, and
  added to the contract guardrail lists.
• Resolves with the applied value, for example { isDarkMode: true }. When
  dark appearance is not available in the embed, the embed does not change and
  the promise rejects with an error message.
• After a successful switch, trigger() stores the value in
  viewConfig.isDarkMode. A later render or pre-render show then sends it
  instead of the value the embed loaded with.

Testing

• 3 unit tests in ts-embed.spec.ts: the reply, the kept appearance, and the rejection.
• Full suite, type-check and size check pass (32.31 kB of 34 kB).
• Tested end to end in a local developer playground.

[gemini-code-assist]

Code Review

This pull request introduces the HostEvent.UpdateTheme event, allowing the embed to switch between dark appearance and its default appearance dynamically without reloading. It adds the UpdateThemeRequest interface, updates the HostEventRequestMap, handles the event in TsEmbed to persist the applied theme state in viewConfig.isDarkMode, and exports the new types. Comprehensive unit tests and JSDoc documentation with examples have also been added. There are no review comments, and we have no feedback to provide.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@thoughtspot/visual-embed-sdk@697

commit: 448a52c