Deliver an event enum with the queue overflow as its own case

The stream's element is now the enum InotifyEvent, and the struct that
describes a change to a watched item is FileSystemEvent. A queue
overflow was an event with descriptor -1 and an empty path that every
consumer had to know about; as a case, the compiler makes them handle
it. The enum is also where failed watches of a growing tree will be
reported, since no call site can catch them.

Sources/Inotify/InotifyEvent.swift

@@ -1,37 +1,9 @@
-import SystemPackage
-
-/// A filesystem event delivered by an ``Inotify`` instance.
-///
-/// When the kernel's event queue overflows, it drops events and reports a
-/// single event whose ``mask`` contains ``InotifyEventMask/queueOverflow``.
-/// Such an event belongs to no watch: its ``watchDescriptor`` is `-1` and
-/// its ``path`` is empty. Consumers that must not miss changes should
-/// rescan the watched trees when they receive one.
-public struct InotifyEvent: Sendable, Hashable, CustomStringConvertible {
-	public let watchDescriptor: Int32
-	public let mask: InotifyEventMask
-	public let cookie: UInt32
-	public let path: FilePath
-	/// Whether the event was produced by the library for an item that already
-	/// existed when its directory became watched, rather than by the kernel.
-	public let synthesized: Bool
-
-	public var description: String {
-		var parts = ["InotifyEvent(wd: \(watchDescriptor), mask: \(mask), path: \"\(path)\""]
-		if cookie != 0 { parts.append("cookie: \(cookie)") }
-		return parts.joined(separator: ", ") + ")"
-	}
-}
-
-extension InotifyEvent {
-	public init(from rawEvent: RawInotifyEvent, inDirectory path: String) {
-		let dirPath = FilePath(path)
-		self.init(
-			watchDescriptor: rawEvent.watchDescriptor,
-			mask: rawEvent.mask,
-			cookie: rawEvent.cookie,
-			path: dirPath.appending(rawEvent.name),
-			synthesized: rawEvent.synthesized
-		)
-	}
+/// What an ``Inotify`` instance delivers: a change to a watched item, or a
+/// condition that affects which changes it can deliver.
+public enum InotifyEvent: Sendable, Hashable {
+	/// A change to a watched file or directory.
+	case fileSystem(FileSystemEvent)
+	/// The kernel's event queue was full, so it dropped events. Consumers
+	/// that must not miss changes should rescan the watched trees.
+	case queueOverflow
 }