huskies: merge 1200 story Low-disk warning: the fleet tells the operator before the disk takes it down

server/src/io/watcher/events.rs

@@ -111,4 +111,28 @@ pub enum WatcherEvent {
         /// Total auto-retry budget shared with the auto-block threshold.
         budget: u32,
     },
+    /// Free disk space on the `/workspace` filesystem crossed a warn/critical
+    /// threshold (story 1200).
+    /// Triggers a rate-limited warning notification to configured chat rooms.
+    DiskSpaceWarning {
+        /// Severity level: `"warn"` or `"critical"`.
+        level: String,
+        /// Free space in bytes at the time of the check.
+        free_bytes: u64,
+        /// Size of the `target/` directory in bytes.
+        target_bytes: u64,
+        /// Size of the `.huskies/worktrees/` directory in bytes.
+        worktrees_bytes: u64,
+        /// Identifier of the sled that observed the reading.
+        host_id: String,
+    },
+    /// Free disk space recovered above the warn threshold plus its recovery
+    /// margin, after a warn/critical warning had been sent (story 1200).
+    /// Triggers a single recovery notification to configured chat rooms.
+    DiskSpaceRecovered {
+        /// Free space in bytes at the time of recovery.
+        free_bytes: u64,
+        /// Identifier of the sled that observed the recovery.
+        host_id: String,
+    },
 }