Rename _isThought parameter in CodeExecutionResultPart initializer

Author: andrewheard

FirebaseAI/Sources/ModelContent.swift

@@ -94,7 +94,7 @@ public struct ModelContent: Equatable, Sendable {
       case let .codeExecutionResult(codeExecutionResult):
         return CodeExecutionResultPart(
           codeExecutionResult: codeExecutionResult,
-          _isThought: part.isThought,
+          isThought: part.isThought,
           thoughtSignature: part.thoughtSignature
         )
       }

FirebaseAI/Sources/Types/Public/Part.swift

@@ -305,14 +305,14 @@ public struct CodeExecutionResultPart: Part {
   public init(outcome: CodeExecutionResultPart.Outcome, output: String) {
     self.init(
       codeExecutionResult: CodeExecutionResult(outcome: outcome.internalOutcome, output: output),
-      _isThought: nil,
+      isThought: nil,
       thoughtSignature: nil
     )
   }
 
-  init(codeExecutionResult: CodeExecutionResult, _isThought: Bool?, thoughtSignature: String?) {
+  init(codeExecutionResult: CodeExecutionResult, isThought: Bool?, thoughtSignature: String?) {
     self.codeExecutionResult = codeExecutionResult
-    self._isThought = _isThought
+    self._isThought = isThought
     self.thoughtSignature = thoughtSignature
   }
 }