feat: register as Android default digital assistant (#757) (#758)

* feat: register as Android default digital assistant

* fix: assistant role request fallback + always-attempt click

* remove: assistant role request row from Settings

The system-level assistant registration stays (VoiceInteractionService
+ ROLE_ASSISTANT, set via system Settings -> Default apps), but the
in-app Settings row is dropped: RequestRoleActivity fails to resolve
the caller on a plain startActivity ('Package name cannot be null or
empty'), so the button was a dead end. Removes the row, the
AssistantRole helper, and the now-unused strings.

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/assistant/AssistantRecognitionService.kt

@@ -0,0 +1,21 @@
+package com.m57.hermescontrol.assistant
+
+import android.content.Intent
+import android.speech.RecognitionService
+
+/**
+ * Stub recognition service. The framework requires a recognition service to
+ * be declared in voice_interaction_service.xml for the assistant component to
+ * be valid (AOSP VoiceInteractionServiceInfo parse error otherwise), but v1
+ * has no speech input — long-press Home just opens the app.
+ */
+class AssistantRecognitionService : RecognitionService() {
+    override fun onStartListening(
+        intent: Intent,
+        callback: Callback,
+    ) = Unit
+
+    override fun onStopListening(callback: Callback) = Unit
+
+    override fun onCancel(callback: Callback) = Unit
+}

app/src/main/java/com/m57/hermescontrol/assistant/AssistantService.kt

@@ -0,0 +1,10 @@
+package com.m57.hermescontrol.assistant
+
+import android.service.voice.VoiceInteractionService
+
+/**
+ * Top-level digital-assistant service. The system keeps this running while
+ * Hermes Mobile is the default assistant; the actual trigger handling lives
+ * in [AssistantSessionService] / [AssistantSession].
+ */
+class AssistantService : VoiceInteractionService()

app/src/main/java/com/m57/hermescontrol/assistant/AssistantSession.kt

@@ -0,0 +1,60 @@
+package com.m57.hermescontrol.assistant
+
+import android.app.assist.AssistContent
+import android.app.assist.AssistStructure
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import android.os.Bundle
+import android.service.voice.VoiceInteractionSession
+import androidx.annotation.RequiresApi
+import com.m57.hermescontrol.MainActivity
+
+/**
+ * Handles a single assistant invocation. There is no voice UI in v1 — every
+ * trigger (long-press Home / corner swipe) simply opens the app in the
+ * foreground, then closes the session.
+ *
+ * [onShow] fires for every invocation; [onHandleAssist] additionally receives
+ * the assist data. Both route to the same guarded launch so the app opens
+ * exactly once per session. The deprecated 3-arg [onHandleAssist] is kept so
+ * the launch works on every supported API level (the framework's
+ * [AssistState] default forwards to it below API 29).
+ */
+class AssistantSession(context: Context) : VoiceInteractionSession(context) {
+    private var launchHandled = false
+
+    override fun onShow(
+        args: Bundle?,
+        showFlags: Int,
+    ) {
+        super.onShow(args, showFlags)
+        launchHermesAndFinish()
+    }
+
+    @Suppress("OVERRIDE_DEPRECATION")
+    override fun onHandleAssist(
+        data: Bundle?,
+        structure: AssistStructure?,
+        content: AssistContent?,
+    ) {
+        launchHermesAndFinish()
+    }
+
+    @RequiresApi(Build.VERSION_CODES.Q)
+    override fun onHandleAssist(state: AssistState) {
+        launchHermesAndFinish()
+    }
+
+    private fun launchHermesAndFinish() {
+        if (launchHandled) return
+        launchHandled = true
+
+        val intent =
+            Intent(context, MainActivity::class.java)
+                .addFlags(Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TOP)
+        context.startActivity(intent)
+
+        finish()
+    }
+}

app/src/main/java/com/m57/hermescontrol/assistant/AssistantSessionService.kt

@@ -0,0 +1,13 @@
+package com.m57.hermescontrol.assistant
+
+import android.os.Bundle
+import android.service.voice.VoiceInteractionSession
+import android.service.voice.VoiceInteractionSessionService
+
+/**
+ * Spawns an [AssistantSession] each time the user invokes the assistant
+ * (long-press Home / corner swipe).
+ */
+class AssistantSessionService : VoiceInteractionSessionService() {
+    override fun onNewSession(args: Bundle?): VoiceInteractionSession = AssistantSession(this)
+}