chore: rename quicproquo → quicprochat in Rust workspace

Rename all crate directories, package names, binary names, proto
package/module paths, ALPN strings, env var prefixes, config filenames,
mDNS service names, and plugin ABI symbols from quicproquo/qpq to
quicprochat/qpc.

crates/quicprochat-sdk/src/events.rs

@@ -0,0 +1,84 @@
+//! Client event system — real-time notifications from the SDK.
+
+/// Events emitted by the SDK to the UI layer.
+#[derive(Debug, Clone)]
+pub enum ClientEvent {
+    /// Successfully connected to the server.
+    Connected,
+
+    /// Disconnected from the server.
+    Disconnected { reason: String },
+
+    /// Registration succeeded.
+    Registered { username: String },
+
+    /// Login succeeded.
+    LoggedIn { username: String },
+
+    /// Logged out.
+    LoggedOut { username: String },
+
+    /// Authentication succeeded.
+    Authenticated { username: String },
+
+    /// A new message was received in a conversation.
+    MessageReceived {
+        conversation_id: [u8; 16],
+        sender_key: Vec<u8>,
+        sender_name: Option<String>,
+        body: String,
+        timestamp_ms: u64,
+    },
+
+    /// A message was sent successfully.
+    MessageSent {
+        conversation_id: [u8; 16],
+        seq: u64,
+    },
+
+    /// A new conversation was created or discovered.
+    ConversationCreated {
+        conversation_id: [u8; 16],
+        display_name: String,
+    },
+
+    /// A member was added to a group conversation.
+    MemberAdded {
+        conversation_id: [u8; 16],
+        member_key: Vec<u8>,
+    },
+
+    /// A member was removed from a group conversation.
+    MemberRemoved {
+        conversation_id: [u8; 16],
+        member_key: Vec<u8>,
+    },
+
+    /// Server-push event received.
+    PushEvent {
+        event_type: u16,
+        payload: Vec<u8>,
+    },
+
+    /// A message was queued in the offline outbox (send failed or disconnected).
+    MessageQueued {
+        outbox_id: i64,
+        conversation_id: [u8; 16],
+    },
+
+    /// Outbox flush completed after reconnect.
+    OutboxFlushed {
+        sent: usize,
+        failed: usize,
+    },
+
+    /// Gap detected in message sequence numbers.
+    MessageGap {
+        conversation_id: [u8; 16],
+        expected_seq: u64,
+        received_seq: u64,
+    },
+
+    /// An error occurred in the background.
+    Error { message: String },
+}