"Test in Playground" is gone from the instruction editor

The Test in Playground button on an instruction block's edit page is removed.

It worked by minting a throwaway draft agent version on the site's first agent every time you clicked it, which piled up orphan drafts in that agent's Versions table and behaved unpredictably on a site with several agents.

To test a block now:

• Open the Playground and pick the agent and version you want: the version has to select the block for it to apply.
• Or create/edit the block from the version editor itself, save that version as a draft, and test that version.

No existing draft version created by the old button is affected; they stay in place and you can archive or ignore them.