docs: link every client in the clients-page chooser + correctness sweep

The "Which should I use?" table on the clients page listed most client
names as bold text, not links — only the Decky plugin and pf-webos were
clickable — so the client references appeared broken. Link each client to
its section (or dedicated page), and fix a stale Windows headless command.

Repo-wide docs correctness/staleness pass against the code:
- steam-deck: client-not-found -> flatpak-not-found (the real backend code)
- install: host cert is punktfunk-host-windows_<ver>.cer, not ..._setup.cer
- configuration: GPU_PRIORITY_CLASS default is auto; 10BIT/444 are default-on
- how-it-works/index: GameStream/Moonlight is opt-in (--gamestream)
- roadmap: clipboard sync is shipped, not planned
- install-client: MSIX/cert artifacts are arch-suffixed (_x64/_arm64)
- requirements: fix garbled 22H2/IddCx sentence
- status: Linux encode also covers AMD/Intel (VAAPI/Vulkan Video)
- automation: add the plugins.changed event
- windows-host: note the optional bundled VB-CABLE virtual mic
- sway: PUNKTFUNK_COMPOSITOR=hyprland is a wlroots-family alias
- running-as-a-service: punktfunk-probe is a source-build-only dev tool

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

docs-site/content/docs/install-client.md

@@ -83,15 +83,17 @@ The Windows client ships as a **signed MSIX** in the package registry. Builds us
 certificate, so you import that certificate once before Windows will install the package.
 
 1. Open the [packages page](https://git.unom.io/unom/-/packages) (generic group), find
-   **`punktfunk-client-windows`**, and download the newest **`.msix`** and its matching **`.cer`**.
+   **`punktfunk-client-windows`**, and download the newest **`.msix`** and its matching **`.cer`** for
+   your CPU — the artifacts are arch-suffixed (`…_x64.msix` / `…_arm64.msix`).
 2. **Trust the publisher certificate**, then install. The MSIX won't install until the certificate is
    trusted — but it's the **same certificate for every release**, so this is genuinely one-time and
    later updates need nothing. In an **admin** PowerShell:
 
    ```powershell
-   Import-Certificate -FilePath .\punktfunk-client-windows.cer `
+   # use the _arm64 files instead on an Arm device
+   Import-Certificate -FilePath .\punktfunk-client-windows_x64.cer `
      -CertStoreLocation Cert:\LocalMachine\TrustedPeople
-   Add-AppxPackage .\punktfunk-client-windows.msix
+   Add-AppxPackage .\punktfunk-client-windows_x64.msix
    ```
 
    If Windows reports a missing dependency, install the