feat: add worker observation websocket proxy

crates/worker-runtime/src/observation.rs

@@ -93,3 +93,62 @@ pub struct RuntimeEventBatch {
     pub events: Vec<RuntimeEvent>,
     pub has_more: bool,
 }
+
+/// Runtime-local cursor for worker-scoped WebSocket observation.
+#[cfg(feature = "ws-server")]
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct WorkerObservationCursor {
+    pub sequence: u64,
+}
+
+#[cfg(feature = "ws-server")]
+impl WorkerObservationCursor {
+    pub const PREFIX: &'static str = "wo";
+
+    pub fn new(sequence: u64) -> Self {
+        Self { sequence }
+    }
+
+    pub fn zero() -> Self {
+        Self { sequence: 0 }
+    }
+
+    pub fn encode(self) -> String {
+        format!("{}_{:016x}", Self::PREFIX, self.sequence)
+    }
+
+    pub fn decode(value: &str) -> Option<Self> {
+        let encoded = value.strip_prefix("wo_")?;
+        if encoded.len() != 16 {
+            return None;
+        }
+        u64::from_str_radix(encoded, 16)
+            .ok()
+            .map(|sequence| Self { sequence })
+    }
+}
+
+/// One protocol event observed from a runtime Worker.
+#[cfg(feature = "ws-server")]
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub struct WorkerObservationEvent {
+    pub cursor: String,
+    pub event_id: String,
+    pub sequence: u64,
+    pub worker_ref: WorkerRef,
+    pub payload: protocol::Event,
+}
+
+#[cfg(feature = "ws-server")]
+impl WorkerObservationEvent {
+    pub fn new(sequence: u64, worker_ref: WorkerRef, payload: protocol::Event) -> Self {
+        let cursor = WorkerObservationCursor::new(sequence).encode();
+        Self {
+            event_id: cursor.clone(),
+            cursor,
+            sequence,
+            worker_ref,
+            payload,
+        }
+    }
+}