Slate v2 Library Docs Truth Pass

Goal

Align the library/package front-door docs with the recovered live surfaces.

updated docs/libraries/slate-react/slate.md to use the current readonly callback/value shapes
updated docs/libraries/slate-react/README.md to name the current runtime surface instead of a generic sub-library description
updated docs/libraries/slate-react/hooks.md and docs/libraries/slate-react/react-editor.md to use the current editor/node signatures
updated docs/libraries/slate-history/README.md to name the actual withHistory / HistoryEditor helper surface
updated docs/libraries/slate-history/history.md to match the current HistoryBatch shape and remove the fake History.isHistory(...) claim
updated docs/libraries/slate-react/README.md to name the current runtime surface instead of a generic sub-library description
expanded docs/libraries/slate-hyperscript.md from a one-line stub into a real package front door with current exports and examples
updated packages/slate-hyperscript/Readme.md to match the live package surface and workspace proof lane
updated the package front doors:
- packages/slate/Readme.md
- packages/slate-react/Readme.md
- packages/slate-history/Readme.md