windows probe-only agent + agent version display unification + reality sni from sing-box fragment

Scope B (Windows agent):
- probe.go split into shared core + probe_linux.go (verbatim Linux
  sampler, build-tagged) + probe_windows.go (Win32 sampler: GetSystemTimes
  CPU diff, GlobalMemoryStatusEx, fixed-drive df totals, GetIfTable2
  counted set, MachineGuid boot identity, registry facts; load and
  TCP/UDP counts stay zero - x/sys v0.47.0 exports no wrapper)
- update intents are acknowledged and skipped on Windows (the release
  assets are Linux binaries; Windows nodes update via install-agent.ps1)
- cmd/xui-agent-windows: SCM service host (svc.Run + mgr install/
  uninstall/start/stop) mirroring main.go's agent lifecycle wiring
- install-agent.ps1: downloads the exe, writes probeOnly agent.json,
  registers and starts the service, rerun-safe

Scope C (version display):
- config.GetAgentDisplayVersion (and the master getter) compose from
  the bare number so a V-form injection no longer doubles the letter
  (AV2.1.0 -> A2.1.0)
- node list view repairs stored AV-prefixed reports at assembly so
  deployed agents read uniformly without an update

Scope D (production fix):
- share-link reality sni: when the inbound has a sing-box fragment,
  sni is the fragment's tls.server_name - the only name the sing-box
  REALITY server serves. The previous rule picked a uniformly random
  serverNames entry per generation, which xray tolerated but sing-box
  refuses as an invalid connection. sid keeps its random pick: the
  converter carries the whole shortIds list into the fragment, so
  every listed sid is served.

internal/config/config.go

@@ -125,16 +125,30 @@ func GetDisplayVersion() string {
 	return defaultDisplayVersion
 }
 
+// bareDisplayVersion is GetDisplayVersion without a single leading
+// V/v. Release builds inject the number either bare ("2.1.0") or in
+// the master's V-form ("V2.1.0"); the letter-prefixed getters below
+// must compose from the bare form so the letter never doubles
+// ("VV2.1.0" / "AV2.1.0" — the latter is what agent rows showed when
+// the V-form was injected).
+func bareDisplayVersion() string {
+	v := GetDisplayVersion()
+	if len(v) > 1 && (v[0] == 'V' || v[0] == 'v') {
+		return v[1:]
+	}
+	return v
+}
+
 // GetMasterDisplayVersion is the master's display version ("V1.0.0"),
 // shown in the panel's version slot.
 func GetMasterDisplayVersion() string {
-	return "V" + GetDisplayVersion()
+	return "V" + bareDisplayVersion()
 }
 
 // GetAgentDisplayVersion is the agent's display version ("A1.0.0"),
 // reported in agent telemetry and shown on agent node rows.
 func GetAgentDisplayVersion() string {
-	return "A" + GetDisplayVersion()
+	return "A" + bareDisplayVersion()
 }
 
 // ParseDisplayVersion parses a display version into its three numeric

internal/config/config_test.go

@@ -75,6 +75,20 @@ func TestDisplayVersionDefaultsAndOverride(t *testing.T) {
 	if got := GetAgentDisplayVersion(); got != "A1.0.1" {
 		t.Fatalf("injected agent display version = %q, want A1.0.1", got)
 	}
+
+	// A release build may inject the number in the master's V-form:
+	// neither getter may double its letter ("VV1.0.2" / "AV1.0.2").
+	displayVersion = "V1.0.2"
+	if got := GetMasterDisplayVersion(); got != "V1.0.2" {
+		t.Fatalf("V-injected master display version = %q, want V1.0.2", got)
+	}
+	if got := GetAgentDisplayVersion(); got != "A1.0.2" {
+		t.Fatalf("V-injected agent display version = %q, want A1.0.2", got)
+	}
+	displayVersion = "v1.0.3"
+	if got := GetAgentDisplayVersion(); got != "A1.0.3" {
+		t.Fatalf("v-injected agent display version = %q, want A1.0.3", got)
+	}
 }
 
 func TestParseDisplayVersion(t *testing.T) {