feat(desktop): inject window.__OPENKB_DESKTOP__ to enable desktop chrome

The #189 frontend gates desktop-only UI (the in-app TitleBar, offset chrome
cluster) on a `window.__OPENKB_DESKTOP__` flag. Set it from the shell so those
features light up when the UI runs inside Tauri.

The window is now created in setup() via WebviewWindowBuilder with an
initialization_script, instead of declaratively in tauri.conf.json — an init
script runs before page scripts on every navigation, so the flag is present on
the splash and (critically) after we navigate the WebView to the sidecar's
served UI. tauri.conf.json's windows[] is emptied accordingly.

Verified under xvfb (WebKitGTK): with the sidecar serving the new frontend,
the Tauri window renders the desktop TitleBar ("OpenKB Studio — Home", traffic
lights, Local badge) — confirming the flag reaches the page. cargo build clean.

Claude-Session: https://claude.ai/code/session_01KZyUSGAzVL9yxpsWWPv6Y2

Author: claude

desktop/src-tauri/src/main.rs

@@ -68,6 +68,22 @@ fn main() {
     tauri::Builder::default()
         .manage(Sidecar(Mutex::new(None)))
         .setup(|app| {
+            // Create the main window programmatically so we can inject the
+            // desktop-shell flag the frontend checks (window.__OPENKB_DESKTOP__).
+            // It gates the in-app TitleBar and other desktop-only chrome. An
+            // initialization script runs before page scripts on every
+            // navigation, so the flag is present on the splash AND after we
+            // navigate to the sidecar's served UI.
+            tauri::WebviewWindowBuilder::new(
+                app,
+                "main",
+                tauri::WebviewUrl::App("index.html".into()),
+            )
+            .title("OpenKB")
+            .inner_size(1200.0, 800.0)
+            .initialization_script("window.__OPENKB_DESKTOP__ = true;")
+            .build()?;
+
             // Non-fatal: if the sidecar can't start (missing binary, port in
             // use), keep the window up on the splash rather than crashing the
             // app. In `cargo run` dev the bundled sidecar isn't present, so

desktop/src-tauri/tauri.conf.json

@@ -7,16 +7,7 @@
     "frontendDist": "splash"
   },
   "app": {
-    "windows": [
-      {
-        "label": "main",
-        "title": "OpenKB",
-        "width": 1200,
-        "height": 800,
-        "resizable": true,
-        "url": "index.html"
-      }
-    ],
+    "windows": [],
     "security": {
       "csp": null
     }