Test peer notification plural formatting

Split the existing PR change into a smaller reviewable piece.
Original change: chore: retry intermittent baseline reassembly test

app/src/test/kotlin/com/bitchat/android/service/PeerAvailabilityPluralTest.kt

@@ -0,0 +1,39 @@
+package com.bitchat.android.service
+
+import android.icu.text.PluralRules
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import java.io.File
+import java.util.Locale
+
+@RunWith(RobolectricTestRunner::class)
+@Config(sdk = [28], manifest = Config.NONE)
+class PeerAvailabilityPluralTest {
+    @Test
+    fun `plural categories preserve the actual peer count`() {
+        // The JVM suite does not package app resources. Read the shipped catalog,
+        // then select its bucket using Android's ICU rules rather than guessing
+        // that the category named "one" can only describe the number 1.
+        for (qualifier in listOf("fil", "ru", "uk", "fr", "pt-rBR", "bn", "fa", "hi")) {
+            val locale = Locale.forLanguageTag(qualifier.replace("-r", "-"))
+            val strings = File("src/main/res/values-$qualifier/strings.xml").readText()
+            val body = Regex(
+                """<plurals name="notification_active_peers_body">(.*?)</plurals>""",
+                RegexOption.DOT_MATCHES_ALL
+            ).find(strings)!!.groupValues[1]
+            val items = Regex("""<item quantity="([^"]+)">(.*?)</item>""")
+                .findAll(body).associate { it.groupValues[1] to it.groupValues[2] }
+            val rules = PluralRules.forLocale(locale)
+            for (count in listOf(0, 1, 2, 3, 5, 21, 31, 101)) {
+                val category = rules.select(count.toDouble())
+                val template = items[category] ?: items.getValue("other")
+                val message = String.format(locale, template, count)
+                val expected = String.format(locale, "%d", count)
+                assertTrue("$qualifier count $count rendered as $message", message.contains(expected))
+            }
+        }
+    }
+}