Harden runtime diagnostics for milestone 3

Make the milestone 3 runtime story predictable instead of treating doctor, self-check, and startup failures as loosely related surfaces.

Split doctor and self-check into distinct read-only flows, add tri-state diagnostic status with stable IDs and next steps, and reuse that wording in CLI output, service logs, and tray-triggered diagnostics. Add non-mutating config/model probes, a make runtime-check gate, and public recovery/validation docs for the X11 GA roadmap.

Validation: make runtime-check; PYTHONPATH=src python3 -m unittest discover -s tests -p 'test_*.py'; python3 -m py_compile src/*.py tests/*.py; PYTHONPATH=src python3 -m aman doctor --help; PYTHONPATH=src python3 -m aman self-check --help. Leave milestone 3 open in the roadmap until the manual X11 validation rows are filled.

tests/test_aman.py

@@ -47,6 +47,18 @@ class FakeDesktop:
         self.quit_calls += 1
 
 
+class FailingInjectDesktop(FakeDesktop):
+    def inject_text(
+        self,
+        text: str,
+        backend: str,
+        *,
+        remove_transcription_from_clipboard: bool = False,
+    ) -> None:
+        _ = (text, backend, remove_transcription_from_clipboard)
+        raise RuntimeError("xtest unavailable")
+
+
 class FakeSegment:
     def __init__(self, text: str):
         self.text = text
@@ -517,6 +529,37 @@ class DaemonTests(unittest.TestCase):
         self.assertEqual(stream.stop_calls, 1)
         self.assertEqual(stream.close_calls, 1)
 
+    @patch("aman.start_audio_recording", side_effect=RuntimeError("device missing"))
+    def test_record_start_failure_logs_actionable_issue(self, _start_mock):
+        desktop = FakeDesktop()
+        daemon = self._build_daemon(desktop, FakeModel(), verbose=False)
+
+        with self.assertLogs(level="ERROR") as logs:
+            daemon.toggle()
+
+        rendered = "\n".join(logs.output)
+        self.assertIn("audio.input: record start failed: device missing", rendered)
+        self.assertIn("next_step: run `aman doctor --config", rendered)
+
+    @patch("aman.stop_audio_recording", return_value=FakeAudio(8))
+    @patch("aman.start_audio_recording", return_value=(object(), object()))
+    def test_output_failure_logs_actionable_issue(self, _start_mock, _stop_mock):
+        desktop = FailingInjectDesktop()
+        daemon = self._build_daemon(desktop, FakeModel(), verbose=False)
+        daemon._start_stop_worker = (
+            lambda stream, record, trigger, process_audio: daemon._stop_and_process(
+                stream, record, trigger, process_audio
+            )
+        )
+
+        with self.assertLogs(level="ERROR") as logs:
+            daemon.toggle()
+            daemon.toggle()
+
+        rendered = "\n".join(logs.output)
+        self.assertIn("injection.backend: output failed: xtest unavailable", rendered)
+        self.assertIn("next_step: run `aman doctor --config", rendered)
+
     @patch("aman.stop_audio_recording", return_value=FakeAudio(8))
     @patch("aman.start_audio_recording", return_value=(object(), object()))
     def test_ai_processor_receives_active_profile(self, _start_mock, _stop_mock):