docs: fix misleading main.tsx filenames

[fry69]

fix #3476

This removes misleading main.tsx filenames from the documentation examples.

Also repetitive/slightly misleading main.ts filenames got removed unless they are complete copy/paste ready examples including proper import statements.

Usually one complete example with a filename on top of the doc section should be enough. Otherwise ambiguity is intentional, as there are multiple places possible to add code snippets.