feat: [Anki 25.01] handle new deckOptions backend methods

Both are introduced by Anki 25.01

* **deckOptionsReady**
  * Called when deck options WebView is ready to receive requests.
  * This is piped through, but not implemented
* **deckOptionsRequireClose**
  * Force closing the deck options

Introduced in https://redirect.github.com/ankitects/anki/commit/d7fc98d4d87a0e07a228ab36c4ce2b1d7187690c
https://redirect.github.com/ankitects/anki/pull/3571

These methods are part of upstream moving away from
bridge commands, replacing them with HTTP calls
(which we handle with `PostRequestHandler`)

The workflow is now:

* anki.deckOptionsPendingChanges() is called on back press
  * If no changes, deckOptionsRequireClose() is called
  * Otherwise, confirm() is called
    * on OK, deckOptionsRequireClose() is called
    * no-op on cancel

Implementation:
* Handle methods in PostRequestHandler
  * via calling through to DeckOptions
  * document new workflow
  * remove unused methods
  * remove bridgeCommands

Fixes 14438 - 'back' button shows discard dialog
Issue 15788 - Uses a better 'Discard' message

AnkiDroid/src/main/java/com/ichi2/anki/pages/DeckOptions.kt

@@ -30,7 +30,7 @@ import com.ichi2.anki.CollectionManager.withCol
 import com.ichi2.anki.CrashReportService
 import com.ichi2.anki.ProgressContext
 import com.ichi2.anki.R
-import com.ichi2.anki.dialogs.DiscardChangesDialog
+import com.ichi2.anki.SingleFragmentActivity
 import com.ichi2.anki.launchCatchingTask
 import com.ichi2.anki.utils.openUrl
 import com.ichi2.anki.withProgress
@@ -67,28 +67,18 @@ class DeckOptions : PageFragment() {
             override fun handleOnBackPressed() {
                 Timber.v("DeckOptions: requesting the webview to handle the user close request.")
                 webView.evaluateJavascript("anki.deckOptionsPendingChanges()") {
-                    // No callback. Checking whether there are change is asynchronous. Javascript will use the BridgeCommand to request
-                    // Kotlin to either close (if there is no change) or request the user to confirm they want to discard the changes.
+                    // Callback is handled in the WebView:
+                    //  * A 'discard changes' dialog may be shown, using confirm()
+                    //  * if no changes, or changes discarded, `deckOptionsRequireClose` is called
+                    //    which PostRequestHandler handles and calls on this fragment
                 }
             }
         }
 
-    override val bridgeCommands =
-        mapOf<String, () -> Unit>(
-            "confirmDiscardChanges" to {
-                launchCatchingTask {
-                    requestConfirmDiscard()
-                }
-            },
-            "_close" to {
-                actuallyClose()
-            },
-        )
-
     /**
      * Close the view, discarding change if needed.
      */
-    private fun actuallyClose() {
+    fun actuallyClose() {
         onBackFromDeckOptions.isEnabled = false
         Timber.v("webView: navigating back")
         launchCatchingTask {
@@ -97,16 +87,6 @@ class DeckOptions : PageFragment() {
         }
     }
 
-    /**
-     * Request the user to confirm they want to close the options, discarding change. If they accept, do it.
-     */
-    private fun requestConfirmDiscard() {
-        Timber.v("DeckOptions: showing 'discard changes'")
-        DiscardChangesDialog.showDialog(requireActivity()) {
-            actuallyClose()
-        }
-    }
-
     /**
      * Callback used when a modal is opened in the webview. It requests the webview to close it.
      */
@@ -223,6 +203,11 @@ class DeckOptions : PageFragment() {
         webView.evaluateJavascript(closeJs, {})
     }
 
+    fun onWebViewReady() {
+        Timber.d("WebView ready to receive input")
+        // TODO: handle this
+    }
+
     companion object {
         fun getIntent(
             context: Context,
@@ -307,3 +292,26 @@ private fun ProgressContext.toUpdatingCardsString(): String? {
         totalCardsCount = params.total,
     )
 }
+
+private fun FragmentActivity.requireDeckOptionsFragment(): DeckOptions {
+    require(this is SingleFragmentActivity) { "activity must be SingleFragmentActivity" }
+    return requireNotNull(this.fragment as? DeckOptions?) { "fragment must be DeckOptions" }
+}
+
+/**
+ * Called when Deck Options WebView is ready to receive requests.
+ */
+fun FragmentActivity.deckOptionsReady(input: ByteArray): ByteArray {
+    requireDeckOptionsFragment().onWebViewReady()
+    return input
+}
+
+/**
+ * Force closing the deck options
+ *
+ * This is called after a 'discard changes?' dialog is accepted
+ */
+fun FragmentActivity.deckOptionsRequireClose(input: ByteArray): ByteArray {
+    requireDeckOptionsFragment().actuallyClose()
+    return input
+}

AnkiDroid/src/main/java/com/ichi2/anki/pages/PostRequestHandler.kt

@@ -123,6 +123,8 @@ val uiMethods =
             }
         },
         "computeFsrsParams" to { bytes -> lifecycleScope.async { computeFsrsParams(bytes) } },
+        "deckOptionsReady" to { bytes -> lifecycleScope.async { deckOptionsReady(bytes) } },
+        "deckOptionsRequireClose" to { bytes -> lifecycleScope.async { deckOptionsRequireClose(bytes) } },
     )
 
 suspend fun FragmentActivity?.handleUiPostRequest(