A skipped live sign-up must report skipped, not passed

The two live sign-up tests guarded themselves with a bare `return`, so
without `-e live true` they finished immediately and reported PASSED. A
test that did nothing and says it passed is worse than one that did not run:
a suite of those is indistinguishable from a suite that works, which is the
only reason to run it.

`assumeTrue` instead, with the message saying how to opt in. Assumed-out
shows as skipped, so the count reflects what was actually exercised.

The iOS side already had this reasoning written down; Android had the
comment's opposite.

Compiles: :app:compileDebugAndroidTestKotlin.

app/src/androidTest/kotlin/io/flamenet/messenger/app/LiveSignUpFleetTest.kt

@@ -11,6 +11,7 @@ import androidx.compose.ui.test.performTextInput
 import androidx.compose.ui.test.printToString
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.platform.app.InstrumentationRegistry
+import org.junit.Assume.assumeTrue
 import org.junit.Before
 import org.junit.Rule
 import org.junit.Test
@@ -73,15 +74,28 @@ class LiveSignUpFleetTest {
         signOutIfSignedIn()
     }
 
+    /**
+     * 🔴 `assumeTrue`, never a bare `return`.
+     *
+     * A bare return leaves the test reporting PASSED having done nothing, and
+     * a suite of those is indistinguishable from a suite that works — which is
+     * the whole reason to run it. Assumed-out shows as skipped, so the count
+     * tells the truth about what was actually exercised.
+     */
+    private fun requireLiveOptIn() =
+        assumeTrue(
+            "pass -e live true to run these — they create real accounts on accounts.flamenet.io",
+            args.getString("live") == "true")
+
     @Test
     fun signUpOnTheManagedRelay() {
-        if (args.getString("live") != "true") return
+        requireLiveOptIn()
         signUpLive(managed, "m")
     }
 
     @Test
     fun signUpOnASharedSelfHostedRelay() {
-        if (args.getString("live") != "true") return
+        requireLiveOptIn()
         signUpLive(sharedSelfHosted, "s")
     }