update remaining major-version dependencies

Bumps that needed real investigation:

- typescript 5.9 → 6.0
- @types/node 22 → 25 (local node is v24)
- jsdom 27 → 29
- knip 5 → 6
- vercel CLI 50 → 53
- @clack/prompts 0 → 1, satori 0.19 → 0.26 (script-only deps)
- @hugeicons/core-free-icons 3 → 4 (37 import sites unaffected)
- @vercel/config 0 → 0.3 (vercel.ts uses /v1 subpath, still exported)
- prettier-plugin-tailwindcss 0.7 → 0.8

While at it, fix a regression I caused last commit: the new export-from
check on only-screens-and-widgets-may-import-parts was over-broad and
also blocked the legitimate barrel pattern of feature-index re-exporting
hooks/lib. Split the leaf zones: parts stay strictly private (no
re-exports), feature-lib and hook are barrel-reexportable from
feature-index. Tests updated, plugin tests now 174/174.

Skipped (peer-dep blocked or knock-on majors):
- astro 5 → 6: @vite-pwa/astro@1.2.0 (latest) only peers astro ≤ 5
- @astrojs/{node,react,vercel} v10, @vitejs/plugin-react 6: gated by astro 6
- eslint 9 → 10: eslint-plugin-react@7.37.5 (latest) peers eslint ≤ 9.7
- @eslint/js 10: tied to eslint 10

Author: carlassmann