netcfg: version node + enhanced help (all paths described)

New /scheme/netcfg/version returns netstack version string.
Help node expanded to list all known subpaths with descriptions.

All 31 tests pass.

netstack/src/scheme/netcfg/mod.rs

@@ -122,18 +122,24 @@ fn mk_root_node(
     cfg_node! {
         "help" => {
             ro [] || {
-                "summary  — one-read network state\n\
-                 sockets  — active socket list\n\
-                 conntrack — connection tracking stats/list\n\
-                 nat      — NAT bindings and rules\n\
-                 capture  — packet capture facility\n\
-                 sysctl   — kernel tunables\n\
-                 route    — routing table\n\
-                 resolv   — DNS configuration\n\
-                 ifaces   — per-interface config/stats\n"
+                "summary    — one-read network state\n\
+                 sockets    — active socket list (TCP/UDP/ICMP)\n\
+                 conntrack  — connection tracking (stats / list)\n\
+                 nat        — NAT bindings (bindings / stats)\n\
+                 capture    — packet capture (enable/read/filter/count)\n\
+                 sysctl     — kernel tunables (net/ipv4/ip_forward)\n\
+                 route      — routing table (list/add/rm/count/gateway)\n\
+                 resolv     — DNS configuration (nameserver/nameserver6)\n\
+                 ifaces     — per-interface config/stats (eth0/lo/...)\n\
+                 version    — netstack version info\n"
                 .to_string()
             }
         },
+        "version" => {
+            ro [] || {
+                format!("{}\n", env!("CARGO_PKG_VERSION"))
+            }
+        },
         "summary" => {
             ro [devices, route_table, socket_set, ip_forward, filter_table] || {
                 let mut out = String::new();