fix(completion): accept instance-qualified hosts for a bare name in zsh

With several NetBox instances, netssh offers "prod/fsn1-bx1…" for the
typed text "fsn1". compadd discarded these matches because they do not
start with the typed word, so <Tab> found nothing. The matcher
'l:|=*' lets zsh accept text before the typed word; netssh has already
filtered the candidates.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/hook/completion_test.go

@@ -200,7 +200,7 @@ _netssh
 		t.Fatalf("%v\n%s", err, out)
 	}
 	// Directive 36 = NoFileComp|KeepOrder: unsorted host group, no file fallback.
-	want := "describe cache:Manage the cache\ncompadd -V hosts -X %Bhosts%b -- web01 web:02\n"
+	want := "describe cache:Manage the cache\ncompadd -V hosts -X %Bhosts%b -M l:|=* -- web01 web:02\n"
 	if string(out) != want {
 		t.Fatalf("got:\n%s\nwant:\n%s", out, want)
 	}