feat(02-03): client socket, autostart daemon, switch handler, workspace wiring

- Client struct sends JSON requests to daemon over Unix socket
- EnsureDaemon auto-starts the daemon if not running (retry 50ms x 20)
- Switch handler uses FuzzyMatch + SwitchToWorkspace via i3 IPC
- InitWorkspaceResolver wires BuildTerminalWorkspaceMap + ResolveWorkspace
- sysattr_linux.go for Setsid detach on daemon spawn

daemon.go

@@ -151,6 +151,7 @@ type Daemon struct {
 	procDir           string
 	claudeDir         string
 	workspaceResolver func(claudePID int) string // nil = no workspace resolution
+	i3commander       I3Commander
 	pollInterval      time.Duration
 	stopCh            chan struct{}
 	listener          net.Listener
@@ -169,6 +170,21 @@ func NewDaemon(sockPath, procDir, claudeDir string, labels *LabelStore) *Daemon
 	}
 }
 
+// InitWorkspaceResolver sets up i3+X11 workspace resolution.
+// If i3 or X11 is unavailable, logs a warning and continues without workspace info.
+func (d *Daemon) InitWorkspaceResolver(treeProvider I3TreeProvider, x11 X11PIDResolver) {
+	if treeProvider == nil || x11 == nil {
+		return
+	}
+	d.workspaceResolver = func(claudePID int) string {
+		termMap, err := BuildTerminalWorkspaceMap(treeProvider, x11)
+		if err != nil {
+			return ""
+		}
+		return ResolveWorkspace(d.procDir, claudePID, termMap)
+	}
+}
+
 // Start runs the daemon: initial scan, then listens on the Unix socket
 // and polls for sessions in the background.
 func (d *Daemon) Start() error {
@@ -329,6 +345,32 @@ func (d *Daemon) handleConnection(conn net.Conn) {
 		d.registry.mu.Unlock()
 		writeResponse(conn, Response{OK: true})
 
+	case "switch":
+		var args SwitchArgs
+		if err := json.Unmarshal(req.Args, &args); err != nil {
+			writeResponse(conn, Response{Error: "invalid switch args: " + err.Error()})
+			return
+		}
+		sessions := d.registry.List()
+		match := FuzzyMatch(args.Query, sessions)
+		if match == nil {
+			writeResponse(conn, Response{Error: "no session matching: " + args.Query})
+			return
+		}
+		if match.Workspace == "" {
+			writeResponse(conn, Response{Error: "no workspace for session " + match.SessionID})
+			return
+		}
+		if d.i3commander == nil {
+			writeResponse(conn, Response{Error: "i3 commander not available"})
+			return
+		}
+		if err := SwitchToWorkspace(d.i3commander, match.Workspace); err != nil {
+			writeResponse(conn, Response{Error: "switch workspace: " + err.Error()})
+			return
+		}
+		writeResponse(conn, Response{OK: true})
+
 	case "stop":
 		writeResponse(conn, Response{OK: true})
 		d.Stop()