DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.
Plugin option validation now provides more actionable guidance: Plugin option "..." isn't set. Open /plugin manage to configure it, or check that the plugin's userConfig schema declares "...". This helps users quickly fix misconfigured plugins.
Evidence
Plugin error message (search for "isn't set. Open /plugin manage to configure it")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.