an experiment: full javadoc update example

[jshook]

This is what happens when try to backfill some javadocs to stop build warnings from mvn javadoc:jar with agentic tools.

This is an elaborate set of javadocs for us to consider, the first of two options. The next one will be minimal fill-ins only.

This version goes deeper on the changes it makes, adding context, phrasing and some explanatory text even where there are some minor javadoc. It doesn't cover all modules. If we like this, I can expand the coverage.

I've updated the PR to cover the whole project, just as the lighter version does.

[github-actions]

Before you submit for review:

• Does your PR follow guidelines from CONTRIBUTIONS.md?
• Did you summarize what this PR does clearly and concisely?
• Did you include performance data for changes which may be performance impacting?
• Did you include useful docs for any user-facing changes or features?
• Did you include useful javadocs for developer oriented changes, explaining new concepts or key changes?
• Did you trigger and review regression testing results against the base branch via Run Bench Main?
• Did you adhere to the code formatting guidelines (TBD)
• Did you group your changes for easy review, providing meaningful descriptions for each commit?
• Did you ensure that all files contain the correct copyright header?

If you did not complete any of these, then please explain below.

[jshook]

We've agreed on a practical way to bring javadocs in using this method, but in smaller batches. Newer PRs will be forthcoming.