feat: time awareness — Lyra perceives 'now' and how long it's been

She had no clock: current date/time and the gap since Brian last spoke were
invisible between turns, and reflection was timeless. Now:
- lyra/clock.py: wall-clock stamp + coarse human gaps ("3 days")
- chat: inject a 'now' note (date/time + gap since last turn) after her
  self-state — when she is, before the world
- reflect(): feed current time + silence gap into reflection, neutrally —
  prompt invites her to weigh elapsed time "to whatever degree it genuinely
  affects you" (no prescribed feeling; whether silence means anything is left
  to emerge)
- memory.last_exchange_at(): timestamp of the most recent exchange

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_time.py

@@ -0,0 +1,53 @@
+"""Time-awareness: gap humanizing + the 'now' note injected into chat context."""
+from __future__ import annotations
+
+import importlib
+from datetime import timedelta
+
+import pytest
+
+from lyra import clock
+
+
+def test_humanize_gap_scales():
+    ref = clock.now()
+    assert clock.humanize_gap(None) is None
+    assert clock.humanize_gap((ref - timedelta(seconds=10)).isoformat(), ref) == "moments"
+    assert clock.humanize_gap((ref - timedelta(minutes=5)).isoformat(), ref) == "5 minutes"
+    assert clock.humanize_gap((ref - timedelta(hours=3)).isoformat(), ref) == "3 hours"
+    assert clock.humanize_gap((ref - timedelta(days=3)).isoformat(), ref) == "3 days"
+    assert clock.humanize_gap((ref - timedelta(days=21)).isoformat(), ref) == "3 weeks"
+    assert clock.humanize_gap((ref - timedelta(days=90)).isoformat(), ref) == "3 months"
+
+
+def test_humanize_gap_handles_future_and_naive():
+    ref = clock.now()
+    # future timestamp clamps to "moments", never negative
+    assert clock.humanize_gap((ref + timedelta(hours=1)).isoformat(), ref) == "moments"
+    # naive ISO (no tz) is treated as UTC, doesn't crash
+    assert clock.humanize_gap("2026-06-01T00:00:00") is not None
+
+
+@pytest.fixture
+def lyra(tmp_path, monkeypatch):
+    monkeypatch.setenv("LYRA_DB_PATH", str(tmp_path / "test.db"))
+    from lyra import llm
+    monkeypatch.setattr(llm, "embed", lambda texts: [[0.1, 0.2, 0.3] for _ in texts])
+    import lyra.memory as memory
+    importlib.reload(memory)
+    return memory
+
+
+def test_now_note_first_contact(lyra):
+    from lyra import chat
+    note = chat._now_note()["content"]
+    assert "current date and time is" in note
+    assert "first thing Brian has ever said" in note
+
+
+def test_now_note_reports_gap(lyra):
+    memory = lyra
+    memory.remember("s1", "user", "hey")
+    from lyra import chat
+    note = chat._now_note()["content"]
+    assert "since Brian last spoke with you" in note