perf(ui): make @rozenite/ui tree-shakeable

[V3RON]

Description

@rozenite/ui is now tree-shaken in plugin builds: a panel bundles only the components it uses.

• Pure annotations: module-scope calls that Rollup couldn't prove free of side effects are now marked /* @__PURE__ */. That covers 21 compound components built with Object.assign(Root, { … }), 11 cva(...), 6 createContext(...), the cn(...) calls nested in cva arguments, and one new Set. The annotations survive into dist/index.js.
• sideEffects: "sideEffects": ["*.css"] in package.json, so styles.css and fonts.css stay side-effectful.
• Regression test: src/tree-shaking.test.ts bundles the built package with Vite's production build.
  • A Button-only entry may contain only the button component, under 20 kB gzipped.
  • A tokens-and-hooks entry may contain no components at all, under 2 kB.
  • It fails against the old build with 95 extra components.

No component code or API changed.

Related Issue

Closes #556

Context

Before this, importing only Button bundled 96 of the library's 124 component parts and their @base-ui/react dependencies.

Import	Before (min+gzip)	After
Button	110.1 kB	11.0 kB
Dialog	110.1 kB	28.8 kB
tokens / hooks only	110 kB	0.1–0.7 kB

Real panels, gzipped JS from forced builds:

Package	Before	After	Change
network-activity-plugin	470.3 kB	428.3 kB	−9%
sqlite-plugin	455.8 kB	431.2 kB	−5%
storage-plugin	336.7 kB	312.9 kB	−7%
react-navigation-plugin	307.3 kB	219.2 kB	−29%
rhf-plugin	200.2 kB	141.8 kB	−29%
controls-plugin	198.9 kB	160.7 kB	−19%
overlay-plugin	199.9 kB	161.5 kB	−19%
file-system-plugin	239.3 kB	200.9 kB	−16%
feature-flags-plugin	245.4 kB	210.4 kB	−14%
performance-monitor-plugin	228.2 kB	201.5 kB	−12%
require-profiler-plugin	236.0 kB	212.4 kB	−10%
shell	181.4 kB	139.6 kB	−23%
app	189.3 kB	147.5 kB	−22%
vite-plugin dev host	194.4 kB	168.5 kB	−13%

preserveModules (one file per component) was evaluated but not adopted.

• For Rollup and Vite consumers, which covers every Rozenite plugin, the output is identical once the annotations are in.
• It would help third-party Webpack or esbuild consumers: a Button-only bundle goes from 36–45 kB to about 11 kB.
• The cost is 121 files in dist instead of 3. It can be a follow-up if those users matter.

Testing

• git fetch origin main && pnpm checks:affected && pnpm test:affected: passed. The new test takes about 2–3 s and has a 60 s timeout, so it doesn't flake when Turborepo runs suites in parallel.
• pnpm release:plan: passed.
• Visual check: Storybook was built against the tree-shaken dist (not the source alias) and compared with the source build. Dialog, Tabs, Sidebar, Menu, Toast, Split, Select, ConfirmDialog, and the Design refresh panel in dark and light give identical screenshots.
• Built panels: ten plugin panels and the shell render with no JS errors: SQLite, React Navigation, Storage, React Hook Form, Controls, Feature Flags, File System, Performance Monitor and Require Profiler.