[client] Add netbird agent-network ls and env commands

Surface the caller-scoped Agent Network setup on the CLI. Both
commands dial management directly with the active profile's WireGuard
key — the same path foreground login uses — so no daemon proto or
engine wiring is needed for the proof of concept.

netbird agent-network ls prints the proxy endpoint, the authorized
providers, and the allowed models (--json for the raw response).

netbird agent-network env prints POSIX export lines for
Anthropic-compatible tools such as Claude Code, applied with
eval "$(netbird agent-network env)": ANTHROPIC_BASE_URL points at
the account's proxy endpoint and ANTHROPIC_AUTH_TOKEN carries a
placeholder (the proxy authenticates by tunnel peer and injects the
real upstream credentials). A model is never guessed: ANTHROPIC_MODEL
is exported only when exactly one model is allowed or --model pins
one; anything ambiguous is printed as comment lines instead.

"Not available for this peer" is an answer, not an error: both
commands exit 0 with a plain message (on stderr for env, keeping the
eval a harmless no-op).

Linear: NET-1399

client/cmd/root.go

@@ -171,6 +171,9 @@ func init() {
 	rootCmd.AddCommand(debugCmd)
 	rootCmd.AddCommand(profileCmd)
 	rootCmd.AddCommand(exposeCmd)
+	rootCmd.AddCommand(agentNetworkCmd)
+	agentNetworkCmd.AddCommand(agentNetworkLsCmd)
+	agentNetworkCmd.AddCommand(agentNetworkEnvCmd)
 
 	networksCMD.AddCommand(routesListCmd)
 	networksCMD.AddCommand(routesSelectCmd, routesDeselectCmd)