fix: preserve probed MCP tools across session switches

mergeDiscoveredToolingState now carries over probedTools from existing
servers when the config fingerprint is unchanged. The equality check in
syncProjectDiscoveredTooling also strips probedTools before comparing,
so runtime-only probe data never triggers a spurious state replacement.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/AryxAppService.ts

@@ -2348,8 +2348,10 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     left?: DiscoveredToolingState,
     right?: DiscoveredToolingState,
   ): boolean {
-    return JSON.stringify(normalizeDiscoveredToolingState(left).mcpServers)
-      === JSON.stringify(normalizeDiscoveredToolingState(right).mcpServers);
+    const stripRuntime = (servers: DiscoveredMcpServer[]) =>
+      servers.map(({ probedTools: _, ...rest }) => rest);
+    return JSON.stringify(stripRuntime(normalizeDiscoveredToolingState(left).mcpServers))
+      === JSON.stringify(stripRuntime(normalizeDiscoveredToolingState(right).mcpServers));
   }
 
   private equalProjectCustomizationState(

src/shared/domain/discoveredTooling.ts

@@ -122,6 +122,7 @@ export function mergeDiscoveredToolingState(
         return {
           ...server,
           status: existing.status,
+          probedTools: existing.probedTools,
         } satisfies DiscoveredMcpServer;
       }