docs(formatter_yaml): pin EOF blank lines divergence (#25269)

crates/oxc_formatter_yaml/AGENTS.md

@@ -46,6 +46,8 @@ Stream-tail end comments (`write_end_comments`) are the one document-layer excep
 Admission reasons and rules: see FORMATTER_POLICY.md "Known divergences". Current divergences:
 
 - anchor/tag order (prettier#19524): source order is preserved, never reordered
+- EOF blank lines: the file always ends with exactly one newline, like every other formatter crate
+  (`|+` keep-chomped verbatim tails excepted); Prettier YAML alone preserves EOF blank lines verbatim
 - `# prettier-ignore` range (prettier#13008): suppresses exactly one node, never every following node
 - anchor next-line comments (prettier#10518 / #9327): structurally avoided, the positional cursor makes them the next node's leading comments
 - blank lines (prettier#15528): one unified rule:

crates/oxc_formatter_yaml/tests/fixtures/yaml/eof-blank-lines.yaml

@@ -0,0 +1,5 @@
+# DIVERGENCE: the file always ends with exactly one newline (`|+` verbatim
+# tails excepted); Prettier YAML alone keeps EOF blank lines verbatim.
+last: value
+
+

crates/oxc_formatter_yaml/tests/fixtures/yaml/eof-blank-lines.yaml.snap

@@ -0,0 +1,26 @@
+---
+source: crates/oxc_formatter_yaml/tests/fixtures/mod.rs
+---
+==================== Input ====================
+# DIVERGENCE: the file always ends with exactly one newline (`|+` verbatim
+# tails excepted); Prettier YAML alone keeps EOF blank lines verbatim.
+last: value
+
+
+
+==================== Output ====================
+------------------
+{ printWidth: 80 }
+------------------
+# DIVERGENCE: the file always ends with exactly one newline (`|+` verbatim
+# tails excepted); Prettier YAML alone keeps EOF blank lines verbatim.
+last: value
+
+-------------------
+{ printWidth: 100 }
+-------------------
+# DIVERGENCE: the file always ends with exactly one newline (`|+` verbatim
+# tails excepted); Prettier YAML alone keeps EOF blank lines verbatim.
+last: value
+
+===================== End =====================