Fix design system selection persistence

[Sid-Qin]

Summary

• Default the New Project design-system picker to the configured default design system when that system exists in the catalog.
• Preserve explicit user changes, including choosing None, instead of reapplying the default after interaction.
• Keep image/video/audio project creation from inheriting a hidden design-system selection.

Root cause

The New Project panel received defaultDesignSystemId but initialized selectedDsIds to an empty array. As a result, structured project surfaces displayed None — freeform and created projects with designSystemId: null unless the user manually reselected a design system.

User impact

New prototype, deck, template, and other structured projects now visibly start with the configured default design system and persist that selection into project creation. Media surfaces remain design-system-free because their picker is hidden.

Testing

• pnpm --filter @open-design/web test
• pnpm --filter @open-design/web typecheck
• pnpm --filter @open-design/web build
• pnpm guard
• pnpm typecheck
• git diff --check

Closes #603

[lefarcen]

Hi @Sid-Qin! Thanks for this PR — the design system default logic is much clearer now. 👍

Found a couple of edge cases that could affect live-artifact projects and catalog changes while the panel is mounted. See inline below.

[mrcfps]

@Sid-Qin I reviewed the New Project panel changes for default design-system initialization, the touched-state behavior that preserves explicit user choices, the media-surface nulling path, and the new component/helper coverage. The implementation looks consistent with the PR goal, and the helper extraction plus tests make the behavior easier to maintain. Thanks for tightening up this project-creation flow — nice work! 🙌

_{Generated by Looper 0.5.6 · runner=reviewer · agent=opencode}

[alchemistklk]

@Sid-Qin Thanks for the update. Before this can be treated as merge-ready, please resolve all remaining review conversations on this PR.

There are still two unresolved threads in apps/web/src/components/NewProjectPanel.tsx:

1. Live-artifact projects still skip design-system defaults because showDesignSystemPicker does not include live-artifact.
2. Selected design-system IDs are not pruned/validated against the current designSystems catalog, so a stale hidden ID can still be submitted after catalog changes.

Please either address both points in code and then resolve the conversations, or reply in-thread if you believe a conversation should be closed without a code change.

[lefarcen]

Hi @Sid-Qin! 🎉

Thanks for your contribution — this PR has been merged and the design system selection persistence fix is now live.

The implementation now properly defaults the picker to the configured design system and preserves user choices across project creation.

Thanks for making open-design better!
— open-design team