feat(displays): clearer virtual-display preset names + descriptions

"Gaming rig" actually meant a dedicated/headless box you only ever stream from,
which confused users — rename it to "Headless box" and rewrite all five preset
summaries to be scenario-first and shorter (the console cards already show the
mechanics as badges). Updated across the host API summaries (mgmt.rs), the web
console labels (en/de), and the docs table + prose. The internal preset id
`gaming-rig` is unchanged (stable API / stored-policy / test contract).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/punktfunk-host/src/mgmt.rs

@@ -1008,11 +1008,11 @@ struct DisplaySettingsState {
 
 fn preset_summary(id: &str) -> &'static str {
     match id {
-        "default" => "Today's behavior: a short linger absorbs reconnects, the streamed output is the sole desktop, extra clients get their own view.",
-        "gaming-rig" => "Dedicated couch/headless box: the game and its display survive disconnects; whoever connects takes the box over.",
-        "shared-desktop" => "A desktop you also use in person: never blank the real monitors, never keep ghost displays, concurrent viewers each get a view.",
-        "hotdesk" => "One user at a time with fast reattach; a second user is told the box is busy; each device+resolution keeps its own scaling.",
-        "workstation" => "Multi-monitor daily driver: your displays come back exactly where you arranged them, per-client identity, exclusive.",
+        "default" => "Good for most setups. Reconnects resume quickly, the stream is the whole desktop, and extra viewers each get their own screen.",
+        "gaming-rig" => "For a machine with no monitor that you only stream from. The game keeps running when you disconnect, and whoever connects next takes it over.",
+        "shared-desktop" => "For a PC you also use in person. Your real monitors are never blanked or left with a leftover display, and extra viewers each get their own screen.",
+        "hotdesk" => "One person at a time — roam between your own devices with an instant reconnect. Anyone else is told the box is busy.",
+        "workstation" => "Your multi-monitor daily driver. Displays come back exactly where you arranged them, each client keeps its own settings, and the desktop is yours alone.",
         _ => "",
     }
 }