Say what to press when Run was the wrong button

[onatozmenn]

Reported by picking any example and pressing Run.

Twenty-two of the twenty-nine examples are libraries: a module of functions and test blocks, with no main to enter through. Pressing Run on any of them answered no \main` found`, in red, and stopped there.

The compiler is right. The page was unhelpful: it offers four verbs equally for every file and then leaves the reader holding a refusal with no next step, which reads as the page being broken rather than as a fact about the file they just picked.

The refusal now carries a line saying a file with no main is a library, and a button that runs its tests. The line is the page talking and is written as such; the compiler's own answer is above it, unchanged.

Matched on the answer rather than on which example is loaded, so it holds for a program somebody wrote themselves, and it survives the compiler saying it at more length, which deed-lang/deed#789 does.

Checked

calendar → Run:

no `main` found
  Nothing here is wrong: a file with no `main` is a library.
  [Run its tests instead]

The button gives three passes. hello, which does have a main, still runs and prints hello, world.

_{Written with AI assistance.}