Clarify developer guidance.

[davidlehn]

Summary of a comment elsewhere:

The top of the output should be clear: "The following packages have high/critical vulnerabilities and need to be updated: X, Y, Z" <-- the current output requires an enormous amount of developer effort to scan through a wall of text to try to figure out if they need to do anything at all. One line at the top should give clear guidance to developers. They should be able to take action based solely on that one line. Everything else should be in a details object [...]

[davidlehn]

The OSV results summary directly at the top. For example:

Total 16 packages affected by 33 known vulnerabilities (0 Critical, 20 High, 8 Medium, 5 Low, 0 Unknown) from 1 ecosystem.
31 vulnerabilities can be fixed.

Then there are the OSV results, then the npm audit results. The presence of any OSV or audit issues should indicate a developer should look into the issues.

It is often only a large "wall of text" when that project has gotten behind on updates. Which is an indication to fix things. If it's only a few recent issues, the output has usually been short enough to more easily check.