word wrap prev/next links on autodocs (#5867)

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## Why are these changes needed?

Long module names get cut off in autodocs. Fixes (3). I would love to
break the words on dots and underscores, but it doesn't look like theres
a CSS option for that

before:

![image](https://github.com/user-attachments/assets/c2e425db-a197-4174-9af8-1f7a805df307)

after:

![image](https://github.com/user-attachments/assets/dcfc261a-61ca-4072-a28f-3b51e428ef7f)


## Related issue number

#5634 

## Checks

- [ ] I've included any doc changes needed for
<https://microsoft.github.io/autogen/>. See
<https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md> to
build and test documentation locally.
- [ ] I've added tests (if relevant) corresponding to the changes
introduced in this PR.
- [ ] I've made sure all auto checks have passed.

python/packages/autogen-core/docs/src/_static/custom.css

@@ -127,4 +127,10 @@ html[data-theme="light"] .bd-header {
     display: block;
     opacity: 1;
     visibility: visible;
+}
+
+/* Long autodoc module names wrap on prev/next links */
+/* TODO: Should we extend this to the entire site? */
+.prev-next-title {
+  word-break: break-word;
 }