docs(site): make docs-site the knowledge base — status tracker + setup guides

Per the new docs workflow (docs-site = KB layer; repo docs/ keeps design notes):
- Add a canonical Status & Progress tracker (status.md): milestones, per-box live
  state, and a dated progress log — the go-forward place to track progress.
- Add setup guides: GNOME/Mutter host (gnome-box — Secure Boot MOK enroll, the
  libnvidia-gl EGL fix, autologin, screen-lock disable, appliance unit), headless
  KDE box, and Bazzite host (ujust input group, gamescope session, gotchas).
- Roadmap is now canonical in docs-site (synced the skew-handshake section 12
  update); removed the repo docs/roadmap.md copy and repointed README to docs-site.
- Nav (meta.json) + landing cards updated; site builds (bun run build).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs-site/content/docs/index.mdx

@@ -14,8 +14,8 @@ AES-GCM).
 ## Start here
 
 <Cards>
-  <Card title="Project Overview" href="/docs/overview" description="Status, architecture, and milestones at a glance." />
+  <Card title="Status & Progress" href="/docs/status" description="Where the work stands, what's live on each box, and a dated progress log." />
   <Card title="Implementation Plan" href="/docs/implementation-plan" description="The full design: protocol core, milestones, and architecture." />
   <Card title="Roadmap" href="/docs/roadmap" description="Decided next goals and the longer-term bets." />
-  <Card title="Linux Host Setup" href="/docs/linux-setup" description="Bring up the build environment on an NVIDIA-GPU Ubuntu VM." />
+  <Card title="Host Setup" href="/docs/linux-setup" description="Build env + bring-up: Linux, headless KDE, GNOME/Mutter, Bazzite." />
 </Cards>