Publish harness and TUI open-source

initial sync from the monorepo

crates/common/xai-tool-protocol/src/hook.rs

@@ -0,0 +1,22 @@
+//! Hook events delivered from the harness to tools.
+
+use serde::{Deserialize, Serialize};
+
+/// Internally-tagged hook payload. New variants land alongside `Custom`,
+/// which keeps unknown future kinds round-trippable.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(tag = "type")]
+pub enum HookEvent {
+    /// Cancel an in-flight call. The owning `tool_call_id` travels in the
+    /// enclosing `hook` frame.
+    Cancel,
+    Pause,
+    Resume,
+    /// Broadcast to every tool server bound to the session.
+    SessionEnded,
+    /// Forward-compatible escape hatch.
+    Custom {
+        kind: String,
+        payload: serde_json::Value,
+    },
+}