/claim #851

Contributes to #851.

This adds another focused docs-revamp slice for the Cycle.js run packages. It expands the API pages for @cycle/run, @cycle/rxjs-run, and @cycle/most-run with:

• clearer run(main, drivers) lifecycle guidance
• dispose-function usage
• explanations of the main/drivers source-sink contract
• setup() examples for delayed startup and testing/integration code
• setupReusable() guidance for @cycle/run
• stream-library expectations and adaptation notes for xstream, RxJS, and most.js
• mirrored updates in the checked-in HTML wrappers for each page

Verification run locally:

• node --check .scripts/make-api-docs.js
• git diff --check
• embedded-markdown consistency checks for run, rxjs-run, and most-run

I also tried regenerating the rendered API HTML with:

• node .scripts/make-api-docs.js run

That fails in the existing docs toolchain because the installed GitHub tarball for dox throws TypeError: parse is not a function, matching the same pre-existing generator failure seen on the other docs-revamp branches.