Release 4.247.0

Any video in a comment (the owner, 11-13: "full support for our composer to support all video file types"; plan §Z.9 step 3).

• The comment box takes any video. thread.renderThread({ mediaAttachments: true }) draws a box that accepts any video, picture, sound, PDF or text (MP4, MOV, MKV, AVI, WebM, 3GP and the rest; HEIC and AVIF pictures) and says Media's limits: pictures 20 MB, videos 300 MB, sound 50 MB, other files 25 MB. Each file goes to Media's composer attachments as it is picked (POST https://openvibe.media/api/v1/attachments, the viewer's own token; the chip shows the progress), and the form carries the ids in attachments, never the bytes. Media sniffs what the file really is and makes a web copy of a video no browser plays. Only on a post route that reads attachments (Community's, from #439); a page without a viewer token keeps the plain upload. Off by default: nothing changes on a page that does not ask.
• Any box can do it: OpenVibeComposer.mount(host, { media: true }) (composer v3's file queue, first module), or data-ovc-media on a form. The core composer sends each file to Media as it is picked, with Media's limits per kind from one table (pictures 20 MB, videos 300 MB, sound 50 MB, other files 25 MB; the type or the extension guides it, as .mkv often has no type in a browser), says an oversize file's limit in words, and cancels an upload when its chip is removed (a mod's upload(file, onProgress, signal) now gets an AbortSignal). A mod's own uploader still comes first.
• A guest sees what signing in adds (plan §Z.2). The menu's You opens, for someone signed out, with one card: "Sign in to make OpenVibe yours", four lines (your home screen on every site; your feed, messages and notifications; your agents and the AI that comes with your account; your wallet and what you own) and a Sign in button whose link is the bar's own, so it goes to this host's sign-in and comes back. A signed-in person never sees it (test/menu-guest-chrome.test.js).
• A comment's video plays. An attachment from Media (att_…) draws as the network's player (video[data-ov-player], Media's web copy, its first frame as the poster, its own shape and length); one whose copy is still being made shows its first frame and a link to the file; a picture shows, a sound gets a bar. Nothing off openvibe.media/a/ is drawn. ov-thread.js loads player.js and player.css when a thread has a video (content-hashed in THREAD_REV).
• Checks: test/thread-media-attachments.test.js (the box, every kind, URLs off Media refused) and test/comment-video-chrome.test.js (a picked .mkv goes to Media with the viewer's token, the form sends its id and no bytes, a 21 MB picture is refused in words, removing a chip mid-upload cancels it, no token keeps the plain upload, the video plays in the player at 390 px).