Opaque panel header and toolbar; explain empty results

The theme's table header colour is a translucent tint, so rows scrolling
underneath made the column bar unreadable. Paint it over the solid
editor background. An empty search now asks the .NET Solution Launcher
which projects the language server loaded and says so, with a reload
button, instead of a bare "No references found".

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0169iPWwKHZoBTNN9qwXiwqk

README.md

@@ -65,6 +65,13 @@ nothing waits on it. The panel gets the same token *types* but paints them from
 webview is not given the theme’s token colours. Set `coloredReferences.semanticTokens` to `false` for
 grammar-only colouring; results spanning more than 40 files skip it.
 
+## When nothing is found
+
+"No references" can mean the language server never indexed the project. If the
+*.NET Solution Launcher* extension is installed, an empty result asks it which projects
+DotRush has loaded and says so — "the language server has not loaded MyGame.Runtime" —
+with a *Reload Workspace* button, instead of a plain "No references found".
+
 ## Settings
 
 - `coloredReferences.view` — which view `Find All References (Colored)` opens: `document` (default) or `panel`