fix: add mintlify-docs to prettierignore to stop CI loop

The Format Code CI job was reformatting an mdx file, pushing a commit,
which triggered another CI run, creating an infinite loop. Generated
docs content should be ignored by prettier like the docs/ folder.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dawnho

.prettierignore

@@ -7,6 +7,7 @@
 
 # Prettier
 docs
+mintlify-docs
 seam-sdk-playground
 gitbook-plugin
 *.hbs
@@ -213,7 +214,7 @@ $RECYCLE.BIN/
 .LSOverride
 
 # Icon must end with two \r
-Icon
+Icon
 
 # Thumbnails
 ._*