#715 JS/HTML codegen: log runtime errors

• Best to review per commit.
• End-user visible changes:
  • For JS/HTML codegen, runtime errors are now wrapped in more context.
  • For HTML codegen, runtime errors are now logged to the log panel.
  • For JS/HTML codegen, improved type hint consistency in generated JSDocs, by using {...} around types of throws in JSDocs.

Addresses #715