docs: user-facing docs revamp — structured product docs + per-platform setup

Replace the dev/agent-log pages with a proper user-facing doc set:

- Getting Started: Introduction (rewritten), How It Works, Quick Start.
- Host Setup: Requirements, then clean per-platform guides — Ubuntu GNOME,
  Ubuntu KDE, Fedora KDE (new), Bazzite (rewritten) — plus Running as a Service
  (desktop / headless GNOME / headless KDE).
- Connecting: Clients overview, Moonlight, Pairing & Trust.
- Configuration: host.env reference, Host CLI, Troubleshooting.
- The dev/design notes (architecture, roadmap, the deferred design specs, CI)
  move to a clearly-separated "Project & Internals" nav section.

Removes the superseded box-specific pages (gnome-box, headless-box, linux-setup,
overview). status.md (the internal progress tracker, with box IPs) is kept as a
file but dropped from the public nav. Site builds clean.

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

docs-site/content/docs/ubuntu-kde.md

@@ -0,0 +1,58 @@
+---
+title: Ubuntu — KDE Plasma
+description: Set up a punktfunk host on Ubuntu with KDE Plasma (KWin).
+---
+
+Set up a punktfunk host on **Ubuntu** running **KDE Plasma**. The host uses KDE's KWin compositor to
+create a per-client virtual display. Needs **KWin 6.5.6 or newer**.
+
+> New to this? Skim [Requirements](/docs/requirements) first.
+
+## NVIDIA driver, dependencies, and build
+
+These steps are identical to the GNOME guide — follow **steps 1–3** of
+[Ubuntu — GNOME](/docs/ubuntu-gnome#1-nvidia-driver):
+
+1. Install the NVIDIA driver **and** the `libnvidia-gl-<version>` userspace; enable `nvidia-drm
+   modeset=1`; reboot and verify with `nvidia-smi`.
+2. Install the build toolchain and runtime libraries (the same `apt` line).
+3. Clone and `cargo build --release -p punktfunk-host`.
+
+## Configure
+
+The host reads `~/.config/punktfunk/host.env`. For KDE Plasma:
+
+```sh
+mkdir -p ~/.config/punktfunk
+cat > ~/.config/punktfunk/host.env <<'ENV'
+WAYLAND_DISPLAY=wayland-0
+XDG_CURRENT_DESKTOP=KDE
+PUNKTFUNK_COMPOSITOR=kwin
+PUNKTFUNK_VIDEO_SOURCE=virtual
+PUNKTFUNK_ZEROCOPY=1
+PUNKTFUNK_INPUT_BACKEND=libei
+ENV
+```
+
+> Make sure you're on a **KDE Wayland** session (not X11) — the picker on the login screen. The
+> virtual-display path is Wayland-only. See the [Configuration reference](/docs/configuration) for
+> every option.
+
+## Run
+
+From a terminal **inside your Plasma session**:
+
+```sh
+cargo run --release -p punktfunk-host -- serve --native
+```
+
+The host starts listening and advertises itself on the network. Now [connect a client](/docs/clients).
+
+To run it at boot — including fully **headless**, with KWin brought up automatically and no login —
+see [Running as a Service](/docs/running-as-a-service); the headless appliance is built around KDE.
+
+## Troubleshooting
+
+- **KWin too old:** virtual outputs need KWin **≥ 6.5.6**. Check with `kwin_wayland --version`.
+- **No picture / capture fails:** confirm you're on a Wayland session and the NVIDIA GL userspace is
+  installed (`libnvidia-gl-<version>`). More in [Troubleshooting](/docs/troubleshooting).