chore: standardize button and icon button primitives

[harshil-2096]

Summary

• Add compound Button and IconButton APIs
• Require explicit Primary, Secondary, Ghost, or Destructive variants
• Standardize sizes to small, medium, and large
• Migrate all existing button usages
• Remove legacy button class helpers and aliases

How was this tested?

Checklist

• I have read the contributing guidelines
• pnpm build, pnpm test, pnpm typecheck, pnpm lint:ci, and pnpm format:check pass locally
• Tests added/updated where it makes sense
• No hand-edits to generated code (packages/trueforge-sdk, .github/fern/openapi/openapi.json, docs/openapi.json) — fork PRs omit SDK regen; maintainers regenerate after merge
• Docs / .env.example updated if configuration or behavior changed

---

Note

Medium Risk
Large, UI-wide refactor with a breaking public Button/IconButton contract for package consumers; behavior should be equivalent but visual edge cases are possible where custom classNames replaced old icon sizing.

Overview
Introduces a public compound API for Button and IconButton in @truefoundry/trueforge-ui: callers must use Button.Primary, .Secondary, .Ghost, or .Destructive (and matching IconButton.*) instead of a single <Button variant="…" />. Sizes are renamed to small, medium, and large; icon-only controls rely on size="small" plus aspect-square / px-0 overrides where needed.

The auiButtonClass helper is removed; styling lives in the primitives. Every in-package usage (atoms, layouts, settings, composer, tool approval, etc.) is migrated to the new API. outline / default variants are folded into Primary or Secondary as appropriate.

Docs, README exports table, changeset (minor), and tests are updated—including compound variant coverage and a reasoning-effort selector assertion for selected-option hover styling.

^{Reviewed by Cursor Bugbot for commit c59ea8e. Bugbot is set up for automated code reviews on this repo. Configure here.}

[changeset-bot]

🦋 Changeset detected

Latest commit: c59ea8e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@truefoundry/trueforge-ui	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 04f194f. Configure here.}