feat(learn,todo,meditate): dictate through the phone's voice input app (ADR 0038, D18)

On Android the microphone now opens the app handling
RECOGNIZE_SPEECH (FUTO Voice Input, Google's), the default the person
chose in Android, and puts the text it returns where the cursor stood,
as Dictation does; cancelled, nothing. Only where none is installed, or
it can't be opened, does speech_to_text listen in line as before.

halkyon_app: VoiceInputApp (one listen, an answer once closed) on the
channel app.halkyon/voice_input, which DeviceSpeechInput asks first at
every listen, answering SpeechStart.finished so that Dictation doesn't
listen again; speech_to_text isn't touched on that route, so our app
asks for no microphone. SpeechInput.listen and Dictation.start take the
prompt the voice input app shows (the field's hint).

Each app: VoiceInput.kt (queryIntentActivities, startActivityForResult,
the first of EXTRA_RESULTS) attached in MainActivity, which hands it
activity results, and RECOGNIZE_SPEECH among the manifest's queries.
The privacy pages of Learn and Meditate say so.

Our own Whisper and Meditate's dream recordings are dropped (D18).

Whats-New: The microphone now dictates through your phone's voice input app, such as FUTO Voice Input.
Whats-New-De: Das Mikrofon diktiert jetzt über die Spracheingabe-App deines Telefons, etwa FUTO Voice Input.
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/learn/halkyon_learn_flutter/lib/src/feature/assistant/widget/composer.dart

@@ -394,8 +394,11 @@ class _SpeakOrSendState() extends State<SpeakOrSend> {
     final words = HalkyonAppLocalizations.of(context);
     final problem = switch (await _dictation.start(
       language: Localizations.localeOf(context).toLanguageTag(),
+      // Shown by the voice input app, where it shows a prompt (Meditate's ADR 0038, D18).
+      prompt: l10n.assistantSpeak,
     )) {
-      SpeechStart.listening => null,
+      // Listening in line, or the voice input app has listened.
+      SpeechStart.listening || SpeechStart.finished => null,
       // A phone without Google's services has no recogniser installed.
       SpeechStart.noRecognizer => words.speechNoRecognizer,
       SpeechStart.unavailable => l10n.assistantSpeechUnavailable,