Add hermes_audio and draw the mouth from the real waveform

audio_state taps the microphone and the speaker monitor with parec and publishes
levels, a speaking/listening/quiet activity, and trigger-locked waveform windows;
audio itself stays out of ROS. The activity detector calibrates its noise floor
at start-up and absorbs steady noise, so a room at -43 dBFS does not read as
"listening" forever, and it ignores the mic while the robot speaks.

The face arbitrates the state it shows: sleeping (agent side only, so room sound
never wakes a face that means "no agent connected") > speaking > listening >
thinking > idle, and draws the mouth from the real samples while fresh scope data
exists, auto-scaled so a quiet voice is still visible.

Checked: a tone played to the sink shows as `speaking` with the mic ignored. The
microphone-to-mouth path with a live voice is not yet confirmed.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

ros/hermes_face/test/test_render.py

@@ -144,3 +144,41 @@ def test_gaze_is_clamped():
     r = FaceRenderer(seed=0)
     r.set_gaze(50, -50, 0.0)
     assert r._gaze == (1.0, -1.0)
+
+
+def mouth_rows(frame):
+    """Row extent of lit pixels in the mouth band."""
+    band = frame[140:215].astype(np.float32).sum(axis=(1, 2))
+    rows = np.nonzero(band > 0.15 * band.max())[0]
+    return int(rows.max() - rows.min()) if len(rows) else 0
+
+
+def run_scope(kind, state, amp):
+    r = FaceRenderer(state=state, seed=0, jitter=0)
+    t, frame = 0.0, None
+    for _ in range(60):
+        t += 1 / 30
+        r.set_scope(kind, amp * np.sin(np.linspace(0, 8 * np.pi, 256)), t)   # refreshed every frame
+        frame = r.frame(t, 1 / 30)
+    return frame
+
+
+def test_the_mouth_draws_the_real_waveform_and_autoscales_it():
+    big, small = run_scope('speaker', 'speaking', 0.8), run_scope('speaker', 'speaking', 0.02)
+    assert mouth_rows(big) > 25 and mouth_rows(small) > 25    # a quiet voice is still visible
+    assert abs(mouth_rows(big) - mouth_rows(small)) < 8
+
+
+def test_the_mic_waveform_is_drawn_only_while_listening_and_stale_data_is_ignored():
+    listening = mouth_rows(run_scope('mic', 'listening', 0.5))
+    idle = mouth_rows(run_scope('mic', 'idle', 0.5))
+    assert listening > idle + 6
+    r = FaceRenderer(state='speaking', seed=0, jitter=0)
+    r.set_scope('speaker', np.sin(np.linspace(0, 6, 128)), 0.0)
+    frame, _ = run(r, 2)                                      # the scope goes stale: synthetic voice, no crash
+    assert frame.max() > 100
+
+
+def test_unknown_scope_kind_rejected():
+    with pytest.raises(ValueError):
+        FaceRenderer().set_scope('radio', [0.0] * 16, 0.0)