fix scoring: HTTP error checking, context refresh, chunk logging

Check HTTP status from logprobs API (was silently ignoring 500s).
Call publish_context_state() after storing scores so F10 screen
updates. Add chunk size logging for OOM debugging.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/bin/poc-agent.rs

@@ -460,6 +460,7 @@ impl Session {
                             )));
                         }
                     }
+                    agent.publish_context_state();
                 });
                 Command::Handled
             }