Support JsonFormat when using generateOutputSchema

Bug description & Expected Behavior

Enable generateOutputSchema to detect and use @JsonFormat.

Without this support, the MCP server is giving the MCP Inspector an error (confirmed gemini cli also breaks so it may be breaking all clients):

Validation failed: structuredContent does not match tool outputSchema. Validation errors: [$.total: string found, number expected]

Steps to reproduce

1. Define a return response object that contains a BigDecimal that uses the JsonFormat. Example Below.

Minimal Complete Reproducible example

@Data
public class BalancePayload {

    @JsonFormat(shape = JsonFormat.Shape.STRING)
    @Schema(accessMode = AccessMode.READ_ONLY, requiredMode = RequiredMode.REQUIRED, description = "The total amount of the balance.", example = "100")
    private BigDecimal total;

}

@GetMapping(...)
@Operation(...)
@McpTool(generateOutputSchema = true)
public BalancePayload getBalance(...) {
    return new BalancePayload().setTotal(BigDecimal.ONE);
}

Start with the generateOutputSchema handling and the JsonFormat annotation shown in the reproducible example. Reproduce the BigDecimal case with @JsonFormat(shape = JsonFormat.Shape.STRING), then inspect the generated output schema and verify that it represents total as a string so MCP Inspector validation succeeds.