Allow std input

We used to have this feature, got dropped recently accidentally,
can do things like:

`cat text_file_with_prompt.txt | ramalama run smollm:135m`

or

`cat some_doc | ramalama run smollm:135m Explain this document:`

Signed-off-by: Eric Curtin <[email protected]>

Author: ericcurtin

ramalama/chat.py

@@ -74,10 +74,19 @@ def __init__(self, args):
         self.url = f"{args.url}/chat/completions"
 
     def handle_args(self):
-        if self.args.ARGS:
-            self.default(" ".join(self.args.ARGS))
+        prompt = " ".join(self.args.ARGS) if self.args.ARGS else None
+        if not sys.stdin.isatty():
+            stdin = sys.stdin.read()
+            if prompt:
+                prompt += f"\n\n{stdin}"
+            else:
+                prompt = stdin
+
+        if prompt:
+            self.default(prompt)
             self.kills()
             return True
+
         return False
 
     def do_EOF(self, user_content):