chore: eliminate all Kotlin compiler warnings in main source (#877)

* chore: eliminate all Kotlin compiler warnings in main source

* test(chat): fix cross-class coroutine leaks poisoning the unit suite

- ChatUpdateCommandTest: inject FakeSlashUsageStore — the real DataStore
  store inits on real IO threads with a relaxed-mock app (cacheDir NPE)
  and leaks an uncaught exception into the next runTest class.
- ChatUpdateCommandTest + SlashCommandDispatchRpcTest: mock
  ProfileSwitchCoordinator.switched (ChatViewModelTest pattern) — VMs
  otherwise park collectors on the singleton flow that crash later
  classes (ProfileSwitchCoordinatorTest) on stale-Main resumption.

Full suite: 944 tests, 0 failures (was 2 flaky per run).

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/util/LocaleContextWrapper.kt

@@ -31,24 +31,34 @@ object LocaleContextWrapper {
 
             code.contains("-r", ignoreCase = true) -> {
                 val parts = code.split("-r", ignoreCase = true)
-                Locale(parts[0], parts.getOrElse(1) { "" })
+                localeFor(parts[0], parts.getOrElse(1) { "" })
             }
 
             code.contains("-") -> {
                 val parts = code.split("-")
-                Locale(parts[0], parts.getOrElse(1) { "" })
+                localeFor(parts[0], parts.getOrElse(1) { "" })
             }
 
             code.contains("_") -> {
                 val parts = code.split("_")
-                Locale(parts[0], parts.getOrElse(1) { "" })
+                localeFor(parts[0], parts.getOrElse(1) { "" })
             }
 
             else -> {
-                Locale(code)
+                Locale.forLanguageTag(code)
             }
         }
 
+    private fun localeFor(
+        language: String,
+        region: String,
+    ): Locale =
+        if (region.isEmpty()) {
+            Locale.forLanguageTag(language)
+        } else {
+            Locale.forLanguageTag("$language-$region")
+        }
+
     /**
      * Wrap [base] so the configuration carries [locale].
      *