chore: rewrite bundle-size with valof, and budget each import by what it adds

[jo16oh]

Why

• Each bundle was compared with the core's budget plus its increment, so it passed by using the core's unused budget. Every byte the core grew took a byte from every other bundle's room.

  + Enum   1,370 B  ≤ 1024 + 384   (+474 measured, +384 nominal)
  

• The production checks searched the bundle for three development strings and Number.isNaN. Renaming a function or a message silenced them, and new development code went unchecked.

What changed

• Cap the core by its whole size, and every other bundle by what it adds to the measured core (added by Enum +474 B / +640 B).
• Raise the increments to Equals +256, Enum +640 and All +1024. Trait stays at +256.
• Check every bundle by size. DevCodeKeptError fails a bundle whose source reads NODE_ENV while production and development minify to the same size. AddsNothingError fails a bundle that adds no library code to the base.
• Keep the --json keys and shape, so replace-bundle-size-claims reads the same numbers.
• Split scripts/bundle-size.ts into scripts/bundle-size/, modelling the bundles, the measurements and the report as valof values.
• Report failures as better-result Results, adding it as a dev dependency.
• Add pipe, flow and tap in scripts/shared/pipe, with type tests generated for every overload. flow can end in a sink such as GenAwait, which Result.gen takes with yield*.
• Pin the scripts to the released valof through #valof, and check them against src before each release.