refactor(agent): extract claude driver into hive-claude crate

hive-claude/src/sink.rs

@@ -0,0 +1,30 @@
+//! Streaming-output consumer hook.
+
+use serde_json::Value;
+
+/// Consumer callbacks for a claude run's output streams. Every method has a
+/// no-op default, so an implementor overrides only what it needs.
+///
+/// Methods are called synchronously from the stdout/stderr readers as lines
+/// arrive, so keep them cheap — the idiomatic body forwards to a channel or an
+/// event bus rather than blocking. The driver handles sentinel classification
+/// (rate-limit, prompt-too-long, …) itself; a sink only *observes* the stream.
+pub trait Sink {
+    /// A parsed `stream-json` object from stdout (assistant/result/system/…
+    /// event). The driver has already classified it for sentinels.
+    fn on_event(&self, _event: &Value) {}
+
+    /// A stdout line that was not valid JSON — occasional Claude Code CLI
+    /// chatter rather than conversation content.
+    fn on_stdout_line(&self, _line: &str) {}
+
+    /// A stderr line, delivered verbatim. The last several are also retained
+    /// by the driver for [`crate::Error::Exit`].
+    fn on_stderr_line(&self, _line: &str) {}
+}
+
+/// A [`Sink`] that discards everything. Useful for fire-and-forget runs where
+/// only the [`crate::Outcome`] matters.
+pub struct NoopSink;
+
+impl Sink for NoopSink {}