Add file 0xdf00 to KSX6924 file selectors (#213)

* Port CEPASProtocol from Metrodroid to fix APDU framing

Fixes #191

The old FareBot CEPASProtocol manually built APDU commands but omitted
the Le (expected response length) byte, causing cards to reject with
6D00 (instruction not supported). Replaced with Metrodroid's approach
that delegates to ISO7816Protocol.sendRequest() for proper APDU framing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Add file 0xdf00 to KSX6924 file selectors

Metrodroid reads file 0xdf00 (decimal 57088) for T-Money cards in
addition to files 1-5. This file may not exist on all KSX6924 cards,
but ISO7816CardReader handles missing files gracefully.

Ref: metrodroid/.../KSX6924Application.kt:199-204

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Apply ktlintFormat

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Add regression tests for KSX6924 file 0xdf00 support

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: codebutler

app/src/commonMain/kotlin/com/codebutler/farebot/shared/nfc/ISO7816Dispatcher.kt

@@ -108,11 +108,28 @@ object ISO7816Dispatcher {
         return selectors
     }
 
-    private fun buildKSX6924FileSelectors(): List<ISO7816CardReader.FileSelector> =
-        (1..5).map { fileId ->
-            ISO7816CardReader.FileSelector(
-                parentDf = null,
-                fileId = fileId,
+    private fun buildKSX6924FileSelectors(): List<ISO7816CardReader.FileSelector> {
+        val selectors = mutableListOf<ISO7816CardReader.FileSelector>()
+
+        // Files 1-5
+        for (fileId in 1..5) {
+            selectors.add(
+                ISO7816CardReader.FileSelector(
+                    parentDf = null,
+                    fileId = fileId,
+                ),
             )
         }
+
+        // File 0xdf00 (T-Money cards)
+        // This file may not exist on all cards, but ISO7816CardReader handles failures gracefully
+        selectors.add(
+            ISO7816CardReader.FileSelector(
+                parentDf = null,
+                fileId = 0xdf00,
+            ),
+        )
+
+        return selectors
+    }
 }

app/src/commonTest/kotlin/com/codebutler/farebot/test/ISO7816DispatcherTest.kt

@@ -0,0 +1,65 @@
+/*
+ * ISO7816DispatcherTest.kt
+ *
+ * This file is part of FareBot.
+ * Learn more at: https://codebutler.github.io/farebot/
+ *
+ * Copyright (C) 2026 Eric Butler <eric@codebutler.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.codebutler.farebot.test
+
+import com.codebutler.farebot.card.ksx6924.KSX6924Application
+import com.codebutler.farebot.shared.nfc.ISO7816Dispatcher
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+import kotlin.test.assertNull
+import kotlin.test.assertTrue
+
+class ISO7816DispatcherTest {
+    @Test
+    fun testKSX6924FileSelectorsIncludesDf00() {
+        val configs = ISO7816Dispatcher.buildAppConfigs()
+        val ksx6924Config = configs.find { it.type == KSX6924Application.TYPE }
+        assertNotNull(ksx6924Config, "KSX6924 config should be present")
+
+        val fileSelectors = ksx6924Config.fileSelectors
+        val fileIds = fileSelectors.map { it.fileId }
+
+        // Files 1-5 should be present
+        for (fileId in 1..5) {
+            assertTrue(
+                fileId in fileIds,
+                "File selector for file $fileId should be present",
+            )
+        }
+
+        // File 0xdf00 should be present (T-Money cards)
+        assertTrue(
+            0xdf00 in fileIds,
+            "File selector for file 0xdf00 should be present",
+        )
+
+        // Total should be 6 selectors
+        assertEquals(6, fileSelectors.size, "Should have exactly 6 file selectors")
+
+        // All KSX6924 file selectors should have null parentDf
+        for (selector in fileSelectors) {
+            assertNull(selector.parentDf, "KSX6924 file selectors should have null parentDf")
+        }
+    }
+}