cherry-pick(#44054): docs: release notes for v1.65 .NET

Author: dgozman

docs/src/api/class-playwrightassertionexception.md

@@ -1,5 +1,5 @@
 # class: PlaywrightAssertionException
-* since: v1.66
+* since: v1.65
 * langs: csharp
 * extends: [PlaywrightException]
 

docs/src/release-notes-csharp.md

@@ -21,6 +21,21 @@ Console.WriteLine(normalized.ToString());
 ### New APIs
 
 - New option [`option: CDPSession.send.timeout`] in [`method: CDPSession.send`].
+- New [PlaywrightAssertionException] is thrown when a Playwright assertion is not met. It extends [PlaywrightException], so `catch (PlaywrightException)` blocks catch it as well.
+- New `ActionTimeout` and `NavigationTimeout` run settings set the default timeouts of every context that the NUnit, MSTest, xUnit and xUnit v3 base classes create. Set them in the [`.runsettings` file](./test-runners.md#using-the-runsettings-file) or on the command line:
+
+  ```xml
+  <RunSettings>
+    <Playwright>
+      <ActionTimeout>10000</ActionTimeout>
+      <NavigationTimeout>60000</NavigationTimeout>
+    </Playwright>
+  </RunSettings>
+  ```
+
+  ```bash
+  dotnet test -- Playwright.ActionTimeout=10000 Playwright.NavigationTimeout=60000
+  ```
 
 ### Breaking Changes ⚠️
 
@@ -34,6 +49,10 @@ Console.WriteLine(normalized.ToString());
 
 - The `ParamsString` option in [APIRequestContext] requests is now appended to the query that the URL already has, instead of replacing it.
 
+### Announcements
+
+* ⚠️ Playwright for .NET now bundles Node.js 26 instead of Node.js 24. On Linux, Node.js 26 needs the `libatomic1` library.
+
 ### Browser Versions
 
 - Chromium 158.0.8127.18