feat: serial:/size: external matching, exclude Hyprland FALLBACK output

- external list now accepts serial: and size: prefixes; desc: matches
  serial too. Fixes docked-mode deadlock where Hyprland's synthetic
  FALLBACK output (created when the built-in is disabled by a stale
  docked config) was treated as a real external monitor, leaving the
  daemon stuck in docked after undocking.
- modes name resolution gains serial: prefix (resolveSerial).
- add -log-level flag for observability.
- add unit tests for external matching and name resolution.
- update README and example config.

internal/daemon/daemon.go

@@ -183,6 +183,9 @@ func (d *Daemon) pollCheck(ctx context.Context) {
 }
 
 // determineState checks whether any external monitor is physically connected.
+// Synthetic outputs that never represent a real external display (e.g.
+// Hyprland's FALLBACK monitor) are excluded by MatchesExternal, so a stuck
+// docked config cannot keep the daemon in docked mode after undocking.
 func (d *Daemon) determineState(monitors []backend.MonitorInfo) backend.State {
 	for _, m := range monitors {
 		// Skip phantom or disconnected monitors.
@@ -191,7 +194,14 @@ func (d *Daemon) determineState(monitors []backend.MonitorInfo) backend.State {
 		}
 		// A monitor is physically present if it reports non-zero dimensions.
 		if m.Width > 0 && m.Height > 0 {
-			if d.config.MatchesExternal(m.Name, m.Description) {
+			if d.config.MatchesExternal(config.ExternalMonitor{
+				Name:        m.Name,
+				Description: m.Description,
+				Serial:      m.Serial,
+				Width:       m.Width,
+				Height:      m.Height,
+				RefreshRate: m.RefreshRate,
+			}) {
 				return backend.StateDocked
 			}
 		}
@@ -261,11 +271,19 @@ func (d *Daemon) applyState(ctx context.Context, state backend.State) error {
 }
 
 // anyExternalConnected returns true if at least one configured external
-// monitor is physically present.
+// monitor is physically present. Synthetic outputs (e.g. Hyprland's FALLBACK)
+// are excluded via MatchesExternal.
 func (d *Daemon) anyExternalConnected(monitors []backend.MonitorInfo) bool {
 	for _, m := range monitors {
 		if m.Width > 0 && m.Height > 0 && m.Name != "" {
-			if d.config.MatchesExternal(m.Name, m.Description) {
+			if d.config.MatchesExternal(config.ExternalMonitor{
+				Name:        m.Name,
+				Description: m.Description,
+				Serial:      m.Serial,
+				Width:       m.Width,
+				Height:      m.Height,
+				RefreshRate: m.RefreshRate,
+			}) {
 				return true
 			}
 		}