fix(share): default comment panel closed on mobile viewports

[rubenxyz]

Summary

• The share page sidebar (comment panel) was hardcoded to useState(true), causing it to be open by default on all screen sizes
• On mobile devices, this means users see the comment pane instead of the video on first load
• Changed to useState(typeof window !== 'undefined' && window.matchMedia('(min-width: 768px)').matches) so the panel defaults to closed on viewports < 768px

Why

When opening a video share link on mobile (Android/iOS), the first thing visible is the comment panel pulled out from the right, not the video itself. The video is pushed off-screen or to a tiny sliver. This fix makes the panel default to closed on mobile, matching expected behavior.

[ravirajsinh45]

Thanks @rubenxyz — diagnosis is right and the single-asset share path is fixed correctly. Two things before we merge:

1. The folder/project share path has the same bug. Share links have two viewer components: ShareViewer (the one you patched) handles single-asset shares, but folder and project shares route to FolderShareViewer → ShareReviewInner, which has its own copy at apps/web/components/share/folder-share-viewer.tsx:801:

const [sidebarOpen, setSidebarOpen] = React.useState(true)

with the same w-[360px] ... shrink-0 panel at line 924. Opening a folder share on a phone and tapping an asset reproduces exactly the bug you're fixing. Could you apply the same default there?

2. CHANGELOG entry. We track user-facing changes in CHANGELOG.md under ## [Unreleased]. Could you add this to the existing ### Fixed list?

- **Public share links open on the media, not the comment panel, on phones** — the shared asset viewer's comment panel defaulted to open at every screen size, so opening a video share link on a phone showed the comment pane first with the video pushed to a sliver off-screen. The panel now starts closed below the `md` breakpoint (768px) and open above it; it can still be toggled either way.

That rule currently only lives in AGENTS.md, not CONTRIBUTING.md or the PR template — our miss, tracked in #189.

Nit, optional: make the initializer lazy so matchMedia isn't re-evaluated on every render — React.useState(() => typeof window !== 'undefined' && …).

Checked and fine: no hydration risk (ShareViewer only mounts after the client-side share fetch resolves — stage starts at loading), 768px matches Tailwind's default md, CI green.

Two things we'll handle separately, not for this PR: the panel is a fixed w-[360px] shrink-0, so opening it on a phone still squeezes the player (#187); and window.matchMedia isn't stubbed in our vitest/jsdom setup, so we'll add that before this area can get a regression test (#188).

[rubenxyz]

Addressed all three items:

1. Folder-share-viewer parity — applied the same matchMedia default to FolderShareViewer/ShareReviewInnern at folder-share-viewer.tsx:801. Folder/project shares now also default to closed on mobile viewports.

2. CHANGELOG — added entry under [Unreleased] ### Fixed.

3. Lazy initializer — the single-asset path in ShareViewer also now uses React.useState(() => ...) to avoid re-evaluating matchMedia on every render.