Fix whitespace in JSON keys by trimming during parsing (#1727)

This PR addresses issue #1599 where LLM responses sometimes include JSON
with whitespace around keys (e.g., `" answer "` instead of `"answer"`).

The fix:
1. Modifies the JSON parser to trim whitespace from keys during object
parsing
2. Adds a test case that verifies JSON with whitespace in keys parses
correctly

This ensures that when LLMs return JSON with extra spaces around keys,
the JSON will still be parsed correctly without requiring additional
handling.

Closes #1599

---

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---------

Co-authored-by: MentatBot <160964065+MentatBot@users.noreply.github.com>
Co-authored-by: hellovai <vbv@boundaryml.com>

Author: mentatbot[bot]

engine/baml-lib/jsonish/src/deserializer/coercer/ir_ref/coerce_class.rs

@@ -88,7 +88,7 @@ impl TypeCoercer for Class {
                     if let Some(field) = self
                         .fields
                         .iter()
-                        .find(|(name, ..)| name.rendered_name().trim() == key)
+                        .find(|(name, ..)| name.rendered_name().trim() == key.trim())
                     {
                         let scope = ctx.enter_scope(field.0.real_name());
                         let parsed = field.1.coerce(&scope, &field.1, Some(v));

engine/baml-lib/jsonish/src/tests/test_basics.rs

@@ -648,6 +648,40 @@ Then would add a summary of sorts.
     }
 );
 
+test_deserializer!(
+  test_whitespace_in_keys_preserved,
+  r#"
+  class Test {
+      answer Answer
+  }
+  
+  class Answer {
+      content float
+  }
+  "#,
+  r#"{" answer ": {" content ": 78.54}}"#,
+  FieldType::string(),
+  r#"{" answer ": {" content ": 78.54}}"#
+);
+
+// This test verifies that when using class deserialization,
+// field matching happens correctly with whitespace-padded keys
+test_deserializer!(
+  test_class_with_whitespace_keys,
+  r#"
+  class Test {
+      answer Answer
+  }
+  
+  class Answer {
+      content float
+  }
+  "#,
+  r#"{" answer ": {" content ": 78.54}}"#,
+  FieldType::class("Test"),
+  {"answer": {"content": 78.54}}
+);
+
 test_partial_deserializer!(
   test_mal_formed_json_sequence,
   r#"

engine/baml-lib/jsonish/src/tests/test_class.rs

@@ -347,6 +347,28 @@ test_deserializer!(
     }
 );
 
+const CLASS_SIMPLE: &str = r#"
+class SimpleTest {
+    answer Answer
+}
+  
+class Answer {
+    content float
+}
+"#;
+
+test_deserializer!(
+    test_class_with_whitespace_keys,
+    CLASS_SIMPLE,
+    r#"{" answer ": {" content ": 78.54}}"#,
+    FieldType::Class("SimpleTest".to_string()),
+    {
+        "answer": {
+            "content": 78.54
+        }
+    }
+);
+
 const CLASS_WITH_NESTED_CLASS_LIST: &str = r#"
 class Resume {
     name string