Pluginize Design and Video workspaces

[Devin-AXIS]

What changed

• Turn Design Studio and Video Studio into trusted first-party workspace plugin packages.
• Reuse the unified iPolloWork plugin lifecycle for default installation, enablement, uninstall, and reinstall.
• Resolve native workspace entries from installed plugin contributions while preserving the existing Design and Video protocols and UI.
• Preserve session project data when packages are uninstalled, and restore the same projects after reinstall.
• Add focused lifecycle, manifest, UI contribution, and runtime flow coverage.

Why

Design and Video were already isolated work surfaces, but their availability was still hard-wired into the host UI. This change makes them independently installable and removable without introducing a second protocol stack or changing the default user experience.

Validation

• pnpm --dir apps/server typecheck
• bun test apps/server/src/plugin-package-manifest.test.ts apps/server/src/plugin-package-lifecycle.test.ts — 42 passed
• pnpm --filter @ipollowork/app typecheck
• bun test apps/app/tests/plugin-ui-contributions.test.ts apps/app/tests/video-hyperframes-panel.test.ts apps/app/tests/design-studio-bridge.test.ts — 58 passed
• Fraimz official creative plugin flow — passed, including uninstall, reinstall, and project restoration
• git diff origin/main...HEAD --check