Add guidance comments to all sample files

- Added '// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start' to all .cs files
- Provides users with quick access to getting started documentation
- Consistent guidance across all sample files

Author: Arun Sekhar

docs/guides/text/chat/chat_instructions.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text with messages using different roles
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/chat/chat_roles.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text with messages using different roles
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/chat/chat_simpleprompt.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text from a simple prompt
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/responses/responses_fileinput.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Prompt template with file input variable
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/responses/responses_instructions.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text with instructions
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/responses/responses_prompttemplate.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text with a prompt template
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/responses/responses_roles.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text with messages using different roles
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false
 

docs/guides/text/responses/responses_simpleprompt.cs

@@ -1,4 +1,5 @@
 // SAMPLE: Generate text from a simple prompt
+// GUIDANCE: Instructions to run this code: https://aka.ms/oai/net/start 
 #:package OpenAI@2.2.*-*
 #:property PublishAot false