[client] Drop an unreachable guard and fix two stale comments

- loginOverridesInput's nil-message guard cannot be reached: Login
  dereferences the message well before it, in storedLoginConfig.
- The docstring above afterLoginPreCheck described persistLoginOverrides,
  which lives further down the file and now carries its own.
- UpdateConfig's comment named DirectUpdateConfig; the function is
  DirectUpdateOrCreateConfig.

client/internal/profilemanager/config.go

@@ -1059,8 +1059,8 @@ func UpdateConfig(input ConfigInput) (*Config, error) {
 
 	// A UI that round-trips the mask GetConfig hands it back is asking to keep
 	// the stored key, not to set the mask as the new one. UpdateOrCreateConfig
-	// and DirectUpdateConfig already collapse it; this one did not, so the
-	// same round-trip through SetConfig replaced the key with asterisks.
+	// and DirectUpdateOrCreateConfig already collapse it; this one did not, so
+	// the same round-trip through SetConfig replaced the key with asterisks.
 	if isPreSharedKeyHidden(input.PreSharedKey) {
 		input.PreSharedKey = nil
 	}

client/server/server.go

@@ -2602,8 +2602,6 @@ func sendTerminalNotification() error {
 	return wallCmd.Wait()
 }
 
-// persistLoginOverrides writes management URL and pre-shared key from a LoginRequest to the
-// active profile config so that subsequent reads pick them up. Empty/nil values are ignored.
 // afterLoginPreCheck is a seam for tests to run a concurrent config change
 // between Login's first privilege check and the authoritative one.
 var afterLoginPreCheck func()

client/server/update_settings_gate.go

@@ -43,10 +43,6 @@ func configChangeRequested(stored *profilemanager.Config, input profilemanager.C
 // through this builder, so the gate can neither refuse a field the write
 // ignores nor miss one it applies.
 func loginOverridesInput(msg *proto.LoginRequest) profilemanager.ConfigInput {
-	if msg == nil {
-		return profilemanager.ConfigInput{}
-	}
-
 	preSharedKey := msg.OptionalPreSharedKey
 	if preSharedKey != nil && *preSharedKey == "" {
 		preSharedKey = nil