Release: promote the OpenScene downloads to production

[sjungwon03]

Scope

Promote the reviewed dev lineage to main so the OpenScene download links reach production.

Content promoted (13 files): 2913694 — feat: publish OpenScene downloads for macOS, Windows, and Linux (#167). The earlier commits listed by git log origin/main..origin/dev are already on main through the squash merge in #165.

Acceptance criteria

• A release labeled PR from dev into main passes verify and release-promotion and carries a latest-head independent approval before squash merge.
• After the merge, verify on production:
  • https://openscene.app/#download renders a card per platform and links all five v0.3.0 assets.
  • Every download link resolves on GitHub rather than 404ing.
  • https://openscene.app/docs/install and /docs/ko/install render the asset table.
  • No page still claims OpenScene has no packaged installer.

Non-goals

• No code change. This is a promotion of already-reviewed commits.