chore: cut 1.0.0

[david-chau]

Asks release-please for 1.0.0 via a Release-As: 1.0.0 footer, and removes the
pre-major flags that were holding it back.

Why it needed asking

bump-minor-pre-major kept every breaking change at a minor bump — and it was
right to. That is what allowed the API to be curated from 66 exports to 18,
split across four entry points, and moved off the client boundary without
burning major versions on a library nobody had built against yet.

That work is finished, so the flag goes. Past 1.0.0 a BREAKING CHANGE footer
means a major, which is the point of the version.

What 1.0.0 promises

Now written down in DESIGN.md, because a version number is a claim about change:

• The exported names are the contract — asserted exactly by
  index.test.ts and entryPoints.test.ts
• What is not exported may change in a patch — ask for it rather than
  reaching into dist/
• The CSS class names count too, since the stylesheet is opt-in and people
  build on the markup
• Documented behaviour is reliable behaviour — the canonical/display split,
  null never being NaN, the caret rules, grouping following the locale
• What is not promised is stated: numbers above 2^53, digits outside ASCII,
  and the matrix rows nobody has hardware to verify

Branches

Cleaned out first, all verified against merged PRs: two stale remotes and ten
locals deleted. origin/main is the only remote branch left.

State at the cut

1301 unit tests          263 Playwright, 6 projects, 3 operating systems
100% coverage × 4        4/4 entries within size budget
attw green × 4           publint clean       0 vulnerabilities

Seven audits. The first six each found something real — 66 exports nobody chose,
declarations wrong for CommonJS, two critical ARIA violations in the widget the
docs told people to copy, a 'use client' banner that broke the documented
server action, a load-bearing rule with no test, and grouping wrong for every
Indian locale. The seventh found nothing, and a leak hunt found one uncancelled
animation frame that was not a leak.

Merging this produces the release PR for 1.0.0. Merging that one publishes.

🤖 Generated with Claude Code