docs: say the collision check does not compare aliases

DataFusion registers a function under each alias as well as its name,
so an alias matching another declared function's name replaces it
silently. Add it to the cases the check does not catch.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: timsaucer

docs/source/extension-guide/bundles.md

@@ -312,7 +312,7 @@ the one case a rename fixes. Collisions are keyed on position rather than on
 object identity so that passing one extension twice reads as the caller's
 duplicate that it is, rather than as a bundle colliding with itself.
 
-Three cases this does *not* catch:
+Four cases this does *not* catch:
 
 - **Different kinds never collide.** Names are compared within a kind, so a
   scalar function and an aggregate may both be called `normalize`.
@@ -326,6 +326,10 @@ Three cases this does *not* catch:
   shadowing rule above, applied to something you may not have meant to shadow.
   Splitting colliding bundles across two calls therefore does not resolve the
   collision; it hides it. Use two sessions.
+- **Aliases are not compared.** DataFusion registers a function under each of
+  its aliases as well as its name, but only the names are checked. A function
+  whose alias matches another declared function's name replaces it, or is
+  replaced by it, with nothing raised.
 
 Your caller cannot rename your function, so stay out of the way: prefix the
 names with something tied to your library.