[datlechin]

First of three PRs that put the Linux app on the site. Data only: Linux stays prototype in platforms.json, so nothing it adds renders yet. PR 3 flips it to released once every page can say it.

• platforms.json: Linux carries its record before it ships: channel (beta), distributions (Ubuntu 26.04/26.10 via the PPA, Fedora 44/45 via COPR, every other distribution via Flatpak), GNOME 50 floor, x86_64 + arm64, the PPA/COPR/Flatpak commands and the GitHub release file templates, the recorded release 0.1.0-beta.1, UI languages en + vi. Commands and file names are the app README's (linux/README.md:39-116, release_assets.py); the Launchpad and COPR web URLs are not linked because no source states them.
• Types: LinuxPlatform, the ppa/copr/flatpak/packages destinations, linuxPlatform(). Linux enters releasedPlatforms() only when status is released.
• LinuxReleaseService + release:refresh-linux (every 15 min): lists GitHub releases (Linux ships with --latest=false), keeps the newest linux-v* on the channel (beta takes pre-releases), each package's size and SHA-256 digest and the SHA256SUMS link; falls back to the release recorded in platforms.json until GitHub has one.
• release:check compares GitHub linux-v*, the Launchpad PPA, COPR and the Flatpak repository with platforms.json once Linux is released.
• engines.json: a linux object per engine (tested with the tested server releases, untested, blocked, none) with evidence lines in TableProApp/TablePro: 11 tested, 6 untested, Oracle blocked, 19 none.
• Feature pages' "Where it works" rows: linux + linuxNote on all 69 rows in 12 locales (17 yes, 19 partial, 33 no; every paid feature is no on Linux). Not rendered yet.
• facts.json: Linux Safe Mode levels, AI providers, MCP tools, import/export formats and result limits; ai and mcp list Linux.
• device.ts: a Linux desktop is linux (Android and ChromeOS stay other). Visible change: a Linux visitor on /download no longer reads "open this page on your Mac".
• JSON-LD: linuxAppNode (#linux-app, free SoftwareApplication).
• Facts checked against the app repo where the fact sheet was wrong: the connect timeout is fixed (only the query timeout is per connection), row editing needs a primary key on Linux, Redis keys change only through commands.
• Checks: pest --exclude-group=ssr 1036 passed, --group=ssr 48 passed, test:js 227 passed, typecheck clean.