feat: add buildMode "ssh" — deploy an SSG site to a remote server via rsync

[vianmora]

What

Adds buildMode: "ssh" to the publisher: build the site as SSG, then rsync the
output to a remote server the user owns, instead of serving it locally.

Closes webstudio-community/webstudio-self-host#7 · sub-issue of webstudio-community/webstudio-self-host#22

How it works

POST /targets/ssh-setup { domain, sshHost, sshUser, sshPath, sshPort?, sshPrivateKey, publicUrl? }
  → /var/work/<domain>/ssh_key      private key, chmod 600, never logged
  → /var/work/<domain>/target.json  { mode:"ssh", sshHost, sshUser, sshPath, sshPort, publicUrl }
  → ssh-keyscan → /var/work/<domain>/known_hosts  (best-effort)

POST /publish { buildId, builderOrigin, buildMode: "ssh" }
  → read target.json   (throws with curl instructions if the site has no target)
  → stop any local runtime/static copy for the site (mode switch → ssh)
  → buildSsgOutput()   (sync → build ssg → vite build → rewrite URLs to publicUrl)
  → rsync -az --delete -e "ssh -p … -i ssh_key -o UserKnownHostsFile=known_hosts
      -o StrictHostKeyChecking=accept-new"  dist/client/  user@host:path/
  → state.json { mode:"ssh", publishDomain, customDomains, sshHost, sshPath, publicUrl }

The publicUrl origin is baked into og: tags and sitemap.xml. It defaults to
the first custom domain, else the wstd hostname.

The publisher does not serve the hostname and writes no Traefik config —
TLS and routing on the remote host are the user's job. Unpublish / mode switch
leave the remote files in place (logged, not deleted).

Changes

• server.mjs:
  • extract buildSsgOutput() — the sync→generate→vite build half shared by
    publishBuild and the new publishBuildSsh
  • hoist transformOutputFiles() and add qualifyPublishDomain() to module scope
  • publishBuildSsh(), readSshTarget(), stopLocalServing()
  • POST /targets/ssh-setup endpoint
  • /publish accepts buildMode: "ssh"; /capabilities → { cloudflare, ssh }
  • teardownSite() handles mode: "ssh"
• Dockerfile: + rsync openssh-client curl jq
• CLAUDE.md, README.md: document the mode

Testing

• node --check server.mjs passes
• SSG pipeline behaviour is unchanged — publishBuild calls the extracted
  buildSsgOutput() with the same publicOrigin it built inline before
• Manual e2e (rsync to a remote box) not yet run on a live stack — flag for review

Companion PRs

• webstudio-fork: buildMode enum + Publish-panel option
• webstudio-self-host: README publish-modes guide

🤖 Generated with Claude Code

https://claude.ai/code/session_01VtPSP1i7NsfKY2DigXV53m

[vianmora]

Superseded by #36, which re-implements the SSH pipeline on top of the renderMode × host model from #35 (host: "ssh" instead of buildMode: "ssh") and bundles the dead-legacy-SSR cleanup + buildSsgOutput() extraction.