test(napplet): read the shell resource where a resource can be read

`shellTemplateKeepsTheOpaqueIframeAndSourceChecks` sat in `commonTest`, so it ran
on both targets: green under `:commons:jvmTest`, and red under
`:commons:testAndroidHostTest` with

    MissingResourceException: ... files/napplet/shell.html.
    Android context is not initialized.

`NappletWebContract.shellHtml()` goes through Compose Resources, whose Android
reader needs an initialised `Context`. A host unit test has none and commons does
not use Robolectric, so the same assertion was red or green depending only on
which target happened to run it. That is the worst shape for a test: it fails on
a developer's machine having passed in whatever ran last, and it kept the whole
module red regardless of the change under review.

Moved to `jvmTest` as `NappletShellResourceTest`. Nothing about it is
platform-specific -- `shell.html` is one shared file, so reading it once on the
JVM checks its contents everywhere. What is genuinely not covered is the Android
resource plumbing, which needs a `Context`; that wants an instrumented test, and
the KDoc says so rather than leaving the gap silent.

The other two contract tests never touch a resource and stay in `commonTest`,
still running on both targets. `:commons:testAndroidHostTest` now passes 1530
tests with no failures, and `:commons:jvmTest` 1913 -- the shell assertion among
them, so it is still enforced.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wwk8tDEaEvsNoGbtrjZavz

commons/src/commonTest/kotlin/com/vitorpamplona/amethyst/commons/napplet/NappletWebContractTest.kt

@@ -20,7 +20,6 @@
  */
 package com.vitorpamplona.amethyst.commons.napplet
 
-import kotlinx.coroutines.test.runTest
 import kotlin.test.Test
 import kotlin.test.assertContains
 import kotlin.test.assertFalse
@@ -64,16 +63,4 @@ class NappletWebContractTest {
         assertContains(csp, "form-action 'none'")
         assertFalse(csp.contains("'self'"))
     }
-
-    @Test
-    fun shellTemplateKeepsTheOpaqueIframeAndSourceChecks() =
-        runTest {
-            val shell = NappletWebContract.shellHtml().decodeToString()
-
-            assertContains(shell, "sandbox=\"${NappletWebContract.APP_SANDBOX_PLACEHOLDER}\"")
-            assertContains(shell, NappletWebContract.APP_BOOTSTRAP_PLACEHOLDER)
-            assertContains(shell, "e.source !== iframe.contentWindow")
-            assertContains(shell, "iframe.contentWindow.postMessage(msg, '*')")
-            assertFalse(shell.contains("allow-same-origin"))
-        }
 }

commons/src/jvmTest/kotlin/com/vitorpamplona/amethyst/commons/napplet/NappletShellResourceTest.kt

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.commons.napplet
+
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertContains
+import kotlin.test.assertFalse
+
+/**
+ * The shell page's own contents, asserted where the resource can actually be read.
+ *
+ * This lives in `jvmTest` rather than `commonTest` because [NappletWebContract.shellHtml] goes
+ * through Compose Resources, and that reader needs an initialised Android `Context` on the
+ * android target. A host unit test has none, so running this in `commonTest` failed
+ * `:commons:testAndroidHostTest` with `MissingResourceException` while passing `:commons:jvmTest`
+ * — the same assertion, red or green depending only on which target ran it.
+ *
+ * Nothing about the assertions is platform-specific: `shell.html` is one shared file, so reading
+ * it once on the JVM checks its contents everywhere. What is *not* covered here is the Android
+ * resource plumbing itself, which needs a `Context` — an instrumented test, or Robolectric, which
+ * commons does not use.
+ *
+ * The rest of the contract's tests stay in `commonTest` and still run on both targets; they never
+ * touch a resource.
+ */
+class NappletShellResourceTest {
+    @Test
+    fun shellTemplateKeepsTheOpaqueIframeAndSourceChecks() =
+        runTest {
+            val shell = NappletWebContract.shellHtml().decodeToString()
+
+            assertContains(shell, "sandbox=\"${NappletWebContract.APP_SANDBOX_PLACEHOLDER}\"")
+            assertContains(shell, NappletWebContract.APP_BOOTSTRAP_PLACEHOLDER)
+            assertContains(shell, "e.source !== iframe.contentWindow")
+            assertContains(shell, "iframe.contentWindow.postMessage(msg, '*')")
+            assertFalse(shell.contains("allow-same-origin"))
+        }
+}