feat: Add per-app proxy (Split Tunneling) for desktop platforms

- Add PerAppProxyOptions struct with Mode, IncludedApplications, ExcludedApplications
- Implement routing rules for include/exclude modes
- Include mode: selected apps use VPN, others go direct
- Exclude mode: selected apps bypass VPN, others use VPN
- Only active on non-Android platforms (Windows, Linux, macOS)
- Logging added for debugging per-app routing decisions

Part of v1.7.6 Split Tunneling feature

config/config.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	C "github.com/sagernet/sing-box/constant"
+	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
 	dns "github.com/sagernet/sing-dns"
 )
@@ -494,6 +495,53 @@ func setRoutingOptions(options *option.Options, opt *HiddifyOptions) {
 			},
 		)
 	}
+	
+	// Per-App Proxy for Desktop platforms (Windows, Linux, macOS)
+	if runtime.GOOS != "android" {
+		if opt.PerAppProxyOptions.Mode == "include" && len(opt.PerAppProxyOptions.IncludedApplications) > 0 {
+			// Mode: Only selected apps use VPN
+			log.Info("[Per-App] Mode: include - ", len(opt.PerAppProxyOptions.IncludedApplications), " apps will use VPN")
+			
+			// Rule 1: Selected apps → VPN
+			routeRules = append(
+				routeRules,
+				option.Rule{
+					Type: C.RuleTypeDefault,
+					DefaultOptions: option.DefaultRule{
+						ProcessName: opt.PerAppProxyOptions.IncludedApplications,
+						Outbound:    OutboundSelectTag,
+					},
+				},
+			)
+			
+			// Rule 2: All other apps → Direct
+			routeRules = append(
+				routeRules,
+				option.Rule{
+					Type: C.RuleTypeDefault,
+					DefaultOptions: option.DefaultRule{
+						Outbound: OutboundDirectTag,
+					},
+				},
+			)
+		} else if opt.PerAppProxyOptions.Mode == "exclude" && len(opt.PerAppProxyOptions.ExcludedApplications) > 0 {
+			// Mode: Excluded apps DON'T use VPN
+			log.Info("[Per-App] Mode: exclude - ", len(opt.PerAppProxyOptions.ExcludedApplications), " apps will bypass VPN")
+			
+			// Rule: Excluded apps → Direct (rest goes through VPN by default)
+			routeRules = append(
+				routeRules,
+				option.Rule{
+					Type: C.RuleTypeDefault,
+					DefaultOptions: option.DefaultRule{
+						ProcessName: opt.PerAppProxyOptions.ExcludedApplications,
+						Outbound:    OutboundDirectTag,
+					},
+				},
+			)
+		}
+	}
+	
 	routeRules = append(routeRules, option.Rule{
 		Type: C.RuleTypeDefault,
 		DefaultOptions: option.DefaultRule{

config/hiddify_option.go

@@ -26,6 +26,13 @@ type HiddifyOptions struct {
 	InboundOptions
 	URLTestOptions
 	RouteOptions
+	PerAppProxyOptions
+}
+
+type PerAppProxyOptions struct {
+	Mode                 string   `json:"per-app-proxy-mode"`        // "off", "include", "exclude"
+	IncludedApplications []string `json:"included-applications"`     // ["chrome.exe", "firefox.exe"]
+	ExcludedApplications []string `json:"excluded-applications"`     // ["steam.exe", "uTorrent.exe"]
 }
 
 type DNSOptions struct {