feat(02-02): implement PPID chain walk + workspace resolution

- ReadPPID parses PPid from /proc/PID/status
- ResolveWorkspace walks PPID chain (max 20 levels) to find terminal workspace
- BuildTerminalWorkspaceMap traverses i3 tree + X11 _NET_WM_PID
- RealX11Resolver wraps xgbutil/ewmh for production use
- Interfaces I3TreeProvider and X11PIDResolver for testability
- Fix unused imports in daemon.go (Rule 3: blocking build)

x11_resolver.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/BurntSushi/xgb/xproto"
+	"github.com/BurntSushi/xgbutil"
+	"github.com/BurntSushi/xgbutil/ewmh"
+)
+
+// RealX11Resolver lit _NET_WM_PID via la connexion X11.
+type RealX11Resolver struct {
+	xu *xgbutil.XUtil
+}
+
+// NewRealX11Resolver ouvre une connexion X11. Retourne une erreur si $DISPLAY est absent.
+func NewRealX11Resolver() (*RealX11Resolver, error) {
+	if os.Getenv("DISPLAY") == "" {
+		return nil, fmt.Errorf("DISPLAY not set, cannot resolve X11 PIDs")
+	}
+	xu, err := xgbutil.NewConn()
+	if err != nil {
+		return nil, fmt.Errorf("X11 connection failed: %w", err)
+	}
+	return &RealX11Resolver{xu: xu}, nil
+}
+
+func (r *RealX11Resolver) GetPID(windowID int64) (int, error) {
+	pid, err := ewmh.WmPidGet(r.xu, xproto.Window(windowID))
+	if err != nil {
+		return 0, err
+	}
+	return int(pid), nil
+}
+
+// Close ferme la connexion X11.
+func (r *RealX11Resolver) Close() {
+	if r.xu != nil {
+		r.xu.Conn().Close()
+	}
+}