Clean up runtimes/ and examples/ — decide what stays

[danbugs]

Summary

The runtimes/ and examples/ directories have grown organically and could use a cleanup pass. Some examples may be redundant, some runtimes may be unused, and the overall organization is a bit messy.

Questions to resolve

• Which examples are essential (demonstrate a unique capability) vs. nice-to-have vs. redundant?
• Are all Dockerfiles in runtimes/ actively used? By which examples?
• Should some examples be consolidated? (e.g., python vs python-agent vs python-agent-driver vs python-tools)
• Is the naming convention consistent and intuitive?
• Should we add a README to examples/ explaining the taxonomy?