Wrap missing primitive tool parameter errors as ToolExecutionException

[arimu1]

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Fixes #6723

Problem

When the model omits an argument for a @Tool method parameter that is a primitive (boolean, int, …), MethodToolCallback resolves it to null and Method.invoke throws a raw IllegalArgumentException. That exception is not an InvocationTargetException, so callMethod did not wrap it as ToolExecutionException. The failure escaped tool-calling machinery and aborted the entire chat turn instead of being handled by ToolExecutionExceptionProcessor.

Solution

1. Early validation in buildMethodArguments: if a looked-up argument is null and the parameter type is primitive, throw ToolExecutionException with an IllegalArgumentException that names the parameter and type (actionable for the model).
2. Safety net in callMethod: catch IllegalArgumentException from Method.invoke and wrap it as ToolExecutionException, mirroring the existing InvocationTargetException handling.

Wrapper types (Boolean, Integer, …) are unchanged: missing values still arrive as null.

Tests

• New MethodToolCallbackPrimitiveArgumentTests (4 tests):
  • missing primitive boolean / int → ToolExecutionException with parameter name
  • missing boxed Boolean still succeeds with null
  • present primitive succeeds
• Also re-ran MethodToolCallbackExceptionHandlingTest and MethodToolCallbackGenericTypesTest

./mvnw -pl spring-ai-model -am test \
  -Dtest=MethodToolCallbackPrimitiveArgumentTests,MethodToolCallbackExceptionHandlingTest,MethodToolCallbackGenericTypesTest \
  -Dsurefire.failIfNoSpecifiedTests=false

Result: 9 tests, 0 failures (Temurin 21). DCO: Signed-off-by present.

Notes

This keeps the fix scoped to the reported MethodToolCallback failure path. Broader “required parameter” enforcement across schema generation and MCP annotations (as discussed on the issue) is left for a follow-up if maintainers want that direction.