refactor(app): the device's speech recognition moves from Learn into halkyon_app, with dictation into a text

Learn's `SpeechInput` and `DeviceSpeechInput` (ADR 0021, D67) are
halkyon_app's now, and its `FakeSpeechInput` is in `testing.dart`, so
Meditate's dream journal (ADR 0038, D15) listens through the same code.
Learn imports them from there and behaves as before: its composer and
its tests are unchanged but for the imports, and `DeviceSpeechInput()`
asks for what it asked before.

`DeviceSpeechInput` takes three options, off by default:
- `preferOnDevice`: on Android, recognition on the device where it can
  (Android 12 on), else offline; should that fail before a word is
  heard (not a pause), it listens as Android otherwise does from then
  on.
- `pauseFor`: how long a pause may last before the recogniser stops.
- `listenFor`: how long one listen may last at most.

`Dictation` writes what is heard where the cursor stands
(`DictationInsertion`: in place of a selection, set apart by a space),
shows the words so far, and listens again after each pause while it is
on, stopping by itself after three listens running heard nothing.

speech_to_text moves from Learn's pubspec to halkyon_app's, the lock
unchanged. Todo, Train and Meditate link the plugin now; their
generated plugin registrants (macOS, Windows) say so. An app declares
the microphone itself, and Todo and Train declare none, so nothing
there can listen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/windows/flutter/generated_plugin_registrant.cc

@@ -10,6 +10,7 @@
 #include <desktop_webview_window/desktop_webview_window_plugin.h>
 #include <file_selector_windows/file_selector_windows.h>
 #include <flutter_secure_storage_windows/flutter_secure_storage_windows_plugin.h>
+#include <speech_to_text_windows/speech_to_text_windows.h>
 #include <url_launcher_windows/url_launcher_windows.h>
 #include <window_to_front/window_to_front_plugin.h>
 
@@ -22,6 +23,8 @@ void RegisterPlugins(flutter::PluginRegistry* registry) {
       registry->GetRegistrarForPlugin("FileSelectorWindows"));
   FlutterSecureStorageWindowsPluginRegisterWithRegistrar(
       registry->GetRegistrarForPlugin("FlutterSecureStorageWindowsPlugin"));
+  SpeechToTextWindowsRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("SpeechToTextWindows"));
   UrlLauncherWindowsRegisterWithRegistrar(
       registry->GetRegistrarForPlugin("UrlLauncherWindows"));
   WindowToFrontPluginRegisterWithRegistrar(

apps/train/halkyon_train_flutter/windows/flutter/generated_plugins.cmake

@@ -7,6 +7,7 @@ list(APPEND FLUTTER_PLUGIN_LIST
   desktop_webview_window
   file_selector_windows
   flutter_secure_storage_windows
+  speech_to_text_windows
   url_launcher_windows
   window_to_front
 )