cmd/tailscaled,feature/conn25,feature/featuretags: add conn25 to featuretags

Package feature/conn25 is excludeable from a build via the featuretag.
Test it is excluded for minimal builds.

Updates #12614

Signed-off-by: Fran Bull <fran@tailscale.com>

feature/buildfeatures/feature_conn25_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_conn25
+
+package buildfeatures
+
+// HasConn25 is whether the binary was built with support for modular feature "Route traffic for configured domains through connector devices".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_conn25" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasConn25 = false

feature/buildfeatures/feature_conn25_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_conn25
+
+package buildfeatures
+
+// HasConn25 is whether the binary was built with support for modular feature "Route traffic for configured domains through connector devices".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_conn25" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasConn25 = true

feature/conn25/conn25.go

@@ -2,6 +2,9 @@
 // SPDX-License-Identifier: BSD-3-Clause
 
 // Package conn25 registers the conn25 feature and implements its associated ipnext.Extension.
+// conn25 will be an app connector like feature that routes traffic for configured domains via
+// connector devices and avoids the "too many routes" pitfall of app connector. It is currently
+// (2026-02-04) some peer API routes for clients to tell connectors about their desired routing.
 package conn25
 
 import (

feature/featuretags/featuretags.go

@@ -138,6 +138,7 @@ var Features = map[FeatureTag]FeatureMeta{
 		Deps: []FeatureTag{"c2n"},
 	},
 	"completion": {Sym: "Completion", Desc: "CLI shell completion"},
+	"conn25":     {Sym: "Conn25", Desc: "Route traffic for configured domains through connector devices"},
 	"cloud":      {Sym: "Cloud", Desc: "detect cloud environment to learn instances IPs and DNS servers"},
 	"dbus": {
 		Sym:                  "DBus",