optimize rendering of results by avoiding console.print

using [line-profiler](https://pypi.org/project/line-profiler/), I found that functions like `render_feature` can be fairly expensive, taking many seconds (cumulatively) to emit their results to the terminal. Digging into this further, it seems that rich's `console.print()` is relatively slow, taking around 100x longer than intermediate string constructions. This means that when we do a lot of little `console.print` calls on parts of a line then performance is poor.

We can optimize this by constructing complete regions or lines up front, and then flushing to the terminal with `console.print`. I think that rich's `Text.append` is still not *very* fast, but its better than doing a terminal write.

Originally we used a StringIO-based strategy of building a large output document and then flushing it in one go (rich-unaware). We might want to migrate back in this direction a little bit.

Start by locating render_feature and the other rendering paths that make many small console.print calls. Use line-profiler to compare terminal output with intermediate string construction, then inspect how Rich Text.append and the earlier StringIO-based strategy could apply. Done means rendering emits larger complete regions or lines with fewer terminal writes while preserving the output.

Written by the indexing model from the issue text.