Summary

• add focused Vitest coverage for interface primitives that are not covered on main: Avatar, Card, Label, Loader, Toggle, Input, and interface manifest tag helpers
• keep the change test-only under plugins/interface/components with no production behavior changes

/claim #71

Verification

• ./node_modules/.bin/vitest.cmd run plugins/interface/components/primitives.test.tsx -> 1 file passed, 8 tests passed
• ./node_modules/.bin/prettier.cmd --check plugins/interface/components/primitives.test.tsx -> passed
• git diff --check -- plugins/interface/components/primitives.test.tsx -> passed

Note: corepack pnpm exec ... triggers pnpm 11’s ignored-builds approval flow in this local Windows shell, so I used the installed project binaries directly after corepack pnpm install completed successfully with approved local builds.