refactor(maglevc): build the CLI on the golang-cli library

Replace maglevc's hand-rolled command-tree CLI with
git.ipng.ch/ipng/golang-cli v1.3.0, mirroring the evpnc refactor. The
tree (commands.go) and the gRPC-status error unwrap (color.go) stay
app-specific; the generic parts — parse tree, completion, '?'-help, the
readline shell, one-shot dispatch, color helpers, and the watch keypress
handler — now come from the library.

- main.go: a single cli.App[grpcapi.MaglevClient] with a Connect
  callback; drops the flag/color-default/dispatch boilerplate.
- commands.go: `type node = cli.Node[grpcapi.MaglevClient]`; label() ->
  cli.Label(); dyn* gain the captured-args parameter the library's
  Dynamic signature carries; runQuit returns cli.ErrQuit.
- watch.go: keypress.WaitForKey replaces the inline cbreak helper.
- color.go: only formatError remains, reading cli.ColorEnabled().
- delete tree.go, complete.go, shell.go.
- tests use the library API; add TestTreeValid (cli.Validate).

Behavior is unchanged except labels/errors now use the library's bright
ANSI palette (was dark); escape lengths are identical so tabwriter
alignment is unaffected. maglevc additionally gains the OpenBSD readline
fix and BSD-correct watch keypress it previously lacked. Builds on linux
and openbsd.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

cmd/client/color.go

@@ -2,42 +2,18 @@
 
 package main
 
-import "strings"
+import (
+	"strings"
 
-const (
-	ansiBlue  = "\x1b[34m"
-	ansiRed   = "\x1b[31m"
-	ansiReset = "\x1b[0m"
+	cli "git.ipng.ch/ipng/golang-cli"
 )
 
-// colorEnabled is set by the -color flag in main.
-var colorEnabled bool
-
-// label wraps s in dark-blue ANSI when color output is enabled.
-//
-// Tabwriter caveat: tabwriter.Writer counts *bytes* per cell, not
-// rendered columns. ANSI escape codes (`\x1b[34m…\x1b[0m`, 11 bytes)
-// inflate a cell's apparent width without affecting what the terminal
-// draws. Two things follow:
-//
-//  1. Key-value layouts where column 1 is *always* labelled and
-//     column 2 is *always* plain (e.g. `show vpp info`) stay aligned,
-//     because every row adds the same 11 bytes to column 1.
-//  2. Multi-column tables where only the *header* row is labelled
-//     drift: the header cells each carry 11 extra bytes that the data
-//     rows don't, so data cells get over-padded. In those tables,
-//     leave the header plain (see runShowVPPLBCounters) and only use
-//     label() for labels that appear uniformly column-wise.
-func label(s string) string {
-	if !colorEnabled {
-		return s
-	}
-	return ansiBlue + s + ansiReset
-}
-
 // formatError returns a user-friendly error string. gRPC status errors are
 // unwrapped to show only the server's message (no "rpc error: code = ..."
-// boilerplate). The result is wrapped in red ANSI when color is enabled.
+// boilerplate). The result is wrapped in red when color is enabled. The label()
+// helper and the ANSI palette now live in the golang-cli library (cli.Label,
+// cli.Red, ...); only this gRPC-specific unwrap stays here, wired in as
+// App.FormatError.
 func formatError(err error) string {
 	msg := err.Error()
 	// google.golang.org/grpc/status errors format as:
@@ -45,8 +21,8 @@ func formatError(err error) string {
 	if i := strings.Index(msg, " desc = "); i >= 0 {
 		msg = msg[i+len(" desc = "):]
 	}
-	if colorEnabled {
-		return ansiRed + msg + ansiReset
+	if cli.ColorEnabled() {
+		return cli.Red + msg + cli.Reset
 	}
 	return msg
 }