fix: remove Reakit peer conflict with React 18-tested tooltip

[mssteuer]

Summary

• Replace the only Reakit source consumer (Tooltip) with the real Ariakit tooltip store/anchor/popup APIs; remove Reakit and its peer-incompatible dependency tree.
• Preserve public React peers (^18.3.0), child refs/events/name/existing description, null behavior, styling and contents; connect the previously ignored forwarded tooltip ref.
• Test actual React/ReactDOM 18.3.1 in StrictMode and Chromium. Add a strict-peer, isolated npm-tarball consumer with a production Vite build and the same browser behavior suite.
• Wire unit/browser/consumer tests into CI on Node 20.19.0 and 22.x, replacing unsupported Node 18 for Vite 7. No publish/deploy workflow changed.

Coordination with #42 — draft pending consolidation

I read the CLICK-908 diff and discussion before preparing this change. It overlaps this exact wrapper with a react-tooltip migration, but keeps Reakit in both package files, so it does not resolve the React 18 peer conflict as written. This draft is a peer-compatibility candidate using the closer successor APIs, not an unnoticed continuation of #42. Maintainers should choose/consolidate the approaches; do not merge both replacements independently. #42 and its branch are untouched.

Verification

• npm ci --legacy-peer-deps=false --strict-peer-deps: passed; actual React/DOM 18.3.1; no Reakit packages.
• npm test: 2 tests passed.
• Rebuilt distribution + Chromium: 2 tests passed (hover/leave/hoverable content, keyboard and non-button anchors, accessible description, Escape retaining focus, normal Tab movement, refs/events, portal, opacity, padding/width and rich content).
• npm run test:consumer: passed; real npm pack, isolated strict installation, no workspace symlink, production Vite bundle and 2 Chromium tests passed.
• Build emits successfully. Standalone typecheck is NOT green: 16 SDK/activity-feed errors match untouched base 08e1b5c byte-for-byte.
• Source-only diff whitespace check passed. Generated FormatJS template literals retain upstream trailing spaces.

Existing limitations / scope

• Styled-components 5 has an independent fresh-resolution Babel-plugin/React-Native peer issue. Fixtures explicitly supply babel-plugin-styled-components 2.1.4, also needed as the existing Vite config's direct build dependency. This is documented, not a global peer override or claim to fix every upstream vulnerability.
• Native Node ESM import (styled default interop) and UMD require (browser window) fail on both untouched base and candidate. This PR verifies the existing browser/Vite target, not SSR support.
• Local npm audit still reports 22 findings in the library development tree; unrelated vulnerability remediation is not bundled here.

Release gate — no release triggered

Registry latest is 2.0.6; master already declares unpublished 2.0.7. After review/consolidation and merge, publish 2.0.7 (or next available patch) through the existing GitHub release-triggered workflow. Then update application lockfile resolutions to the registry release and rerun strict install/build/browser checks. CSPR.click UI 1.12.1 declares design ^2.0.6, so it accepts 2.0.7 without a separate UI release, subject to verifying the actual application's locked version.

Test instructions and caveats: tests/README.md.

Model: gpt-6-astra