feat(notifications): Phase 2.5b per-channel-type renderers

Adds dedicated renderer classes per channel type:

- MeshRenderer produces 1+ chunks <=200 chars with (k/N) counters
  when the payload overflows. Reuses the toggle-label vocabulary
  from the digest. Mesh channels skip re-chunking when the payload
  already carries chunk_index metadata (digest path).
- EmailRenderer produces {subject, body} with structured context
  lines. Plain text only; HTML body is a future polish.
- WebhookRenderer produces a JSON-serializable dict with stable
  schema_version 1.0. Optional fields omitted (not nulled) for
  compactness. Designed for reuse by Phase 2.6.5's MQTT event
  publisher.
- All four channel implementations (MeshBroadcast, MeshDM, Email,
  Webhook) now call their renderer in deliver() before transport.
- New renderer tests cover each renderer in isolation; new channel
  integration tests confirm channels actually call their renderer.

Renderers are pure functions of the payload - no network, no
state, fully testable without mocking I/O. The future MQTT
publisher will instantiate WebhookRenderer directly.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_renderers.py

@@ -0,0 +1,317 @@
+"""Tests for Phase 2.5b per-channel-type renderers."""
+
+import json
+import re
+import time
+
+import pytest
+
+from meshai.notifications.events import NotificationPayload, make_event, make_payload_from_event
+from meshai.notifications.renderers import MeshRenderer, EmailRenderer, WebhookRenderer
+
+
+# ============================================================
+# MESH RENDERER TESTS
+# ============================================================
+
+def test_mesh_render_short_message_single_chunk():
+    """Short message produces a single chunk."""
+    payload = NotificationPayload(
+        message="Test alert",
+        category="test",
+        severity="routine",
+        timestamp=time.time(),
+    )
+    renderer = MeshRenderer()
+    chunks = renderer.render(payload)
+    assert len(chunks) == 1
+    assert "Test alert" in chunks[0]
+
+
+def test_mesh_render_event_type_prefix():
+    """Known event type adds toggle label prefix."""
+    payload = NotificationPayload(
+        message="Severe storm",
+        category="weather_warning",
+        severity="priority",
+        timestamp=time.time(),
+        event_type="weather_warning",
+    )
+    renderer = MeshRenderer()
+    chunks = renderer.render(payload)
+    assert len(chunks) == 1
+    assert chunks[0].startswith("[Weather]")
+
+
+def test_mesh_render_unknown_event_type_no_prefix():
+    """Unknown event type does not add a prefix."""
+    payload = NotificationPayload(
+        message="Hello",
+        category="made_up_thing",
+        severity="routine",
+        timestamp=time.time(),
+        event_type="made_up_thing",
+    )
+    renderer = MeshRenderer()
+    chunks = renderer.render(payload)
+    assert len(chunks) == 1
+    assert not chunks[0].startswith("[")
+
+
+def test_mesh_render_long_message_chunks():
+    """Long message splits into multiple chunks with counters."""
+    # Build a ~500 char message
+    long_message = "This is a very long alert message that should definitely exceed the two hundred character limit. " * 5
+    payload = NotificationPayload(
+        message=long_message,
+        category="weather_warning",
+        severity="priority",
+        timestamp=time.time(),
+        event_type="weather_warning",
+    )
+    renderer = MeshRenderer()
+    chunks = renderer.render(payload)
+
+    assert len(chunks) >= 2
+    for chunk in chunks:
+        assert len(chunk) <= 200, f"Chunk exceeds limit: {len(chunk)} chars"
+    # Check each chunk ends with "(k/N)" counter
+    for chunk in chunks:
+        assert re.search(r"\(\d+/\d+\)$", chunk), f"Missing counter: {chunk}"
+
+
+def test_mesh_render_chunks_preserve_full_content():
+    """Chunking preserves all words from the original message."""
+    # Build a message with distinct tokens
+    words = ["alpha", "bravo", "charlie", "delta", "echo", "foxtrot", "golf",
+             "hotel", "india", "juliet", "kilo", "lima", "mike", "november",
+             "oscar", "papa", "quebec", "romeo", "sierra", "tango", "uniform",
+             "victor", "whiskey", "xray", "yankee", "zulu"]
+    long_message = " ".join(words * 3)  # Repeat to span multiple chunks
+
+    payload = NotificationPayload(
+        message=long_message,
+        category="test",
+        severity="routine",
+        timestamp=time.time(),
+    )
+    renderer = MeshRenderer()
+    chunks = renderer.render(payload)
+
+    # Join all chunks and remove counters
+    combined = " ".join(chunks)
+    combined = re.sub(r"\s*\(\d+/\d+\)", "", combined)
+
+    # Every original word should appear
+    for word in words:
+        assert word in combined, f"Missing word: {word}"
+
+
+def test_mesh_render_no_event_type():
+    """Payload without event_type has no prefix."""
+    payload = NotificationPayload(
+        message="Plain message",
+        category="test",
+        severity="routine",
+        timestamp=time.time(),
+        event_type=None,
+    )
+    renderer = MeshRenderer()
+    chunks = renderer.render(payload)
+    assert len(chunks) == 1
+    assert chunks[0] == "Plain message"
+
+
+# ============================================================
+# EMAIL RENDERER TESTS
+# ============================================================
+
+def test_email_render_subject_includes_severity_and_type():
+    """Subject line includes severity and event type."""
+    payload = NotificationPayload(
+        message="Storm approaching",
+        category="weather_warning",
+        severity="immediate",
+        timestamp=time.time(),
+        event_type="weather_warning",
+    )
+    renderer = EmailRenderer()
+    rendered = renderer.render(payload)
+
+    assert "IMMEDIATE" in rendered["subject"]
+    assert "Weather Warning" in rendered["subject"]
+
+
+def test_email_render_body_includes_message_and_context():
+    """Body includes message and structured context fields."""
+    fixed_time = 1700000000.0  # Known timestamp
+    payload = NotificationPayload(
+        message="Test alert message",
+        category="battery_warning",
+        severity="priority",
+        timestamp=fixed_time,
+        event_type="battery_warning",
+        region="Magic Valley",
+        node_name="BLD-MTN",
+    )
+    renderer = EmailRenderer()
+    rendered = renderer.render(payload)
+    body = rendered["body"]
+
+    assert "Test alert message" in body
+    assert "Magic Valley" in body
+    assert "BLD-MTN" in body
+    assert "priority" in body
+    assert "battery_warning" in body
+    # Check formatted date
+    assert "2023-11-14" in body  # Date part of timestamp
+
+
+def test_email_render_omits_missing_context():
+    """Body omits lines for missing optional fields."""
+    payload = NotificationPayload(
+        message="Minimal alert",
+        category="test",
+        severity="routine",
+        timestamp=time.time(),
+        # No region, no node, no event_type
+    )
+    renderer = EmailRenderer()
+    rendered = renderer.render(payload)
+    body = rendered["body"]
+
+    assert "Minimal alert" in body
+    assert "Severity: routine" in body
+    assert "Region:" not in body
+    assert "Node:" not in body
+    assert "Category:" not in body
+
+
+def test_email_render_includes_source_event():
+    """Body includes source event details when present."""
+    event = make_event(
+        source="weather_adapter",
+        category="weather_warning",
+        severity="priority",
+        title="Severe Storm",
+        summary="Severe storm expected",
+    )
+    payload = make_payload_from_event(event)
+
+    renderer = EmailRenderer()
+    rendered = renderer.render(payload)
+    body = rendered["body"]
+
+    assert "weather_adapter" in body
+    assert "Severe Storm" in body
+
+
+# ============================================================
+# WEBHOOK RENDERER TESTS
+# ============================================================
+
+def test_webhook_render_has_schema_version():
+    """Output includes schema_version field."""
+    payload = NotificationPayload(
+        message="Test",
+        category="test",
+        severity="routine",
+        timestamp=time.time(),
+    )
+    renderer = WebhookRenderer()
+    rendered = renderer.render(payload)
+
+    assert rendered["schema_version"] == "1.0"
+
+
+def test_webhook_render_omits_none_fields():
+    """None optional fields are omitted, not set to null."""
+    payload = NotificationPayload(
+        message="Test message",
+        category="test",
+        severity="routine",
+        timestamp=time.time(),
+        # All optional fields default to None
+    )
+    renderer = WebhookRenderer()
+    rendered = renderer.render(payload)
+
+    # Required fields present
+    assert "message" in rendered
+    assert "severity" in rendered
+    assert "timestamp" in rendered
+    assert "schema_version" in rendered
+
+    # Optional fields omitted
+    assert "node_id" not in rendered
+    assert "region" not in rendered
+    assert "chunk_index" not in rendered
+
+
+def test_webhook_render_includes_source_event_when_present():
+    """source_event dict included when payload has source event."""
+    event = make_event(
+        source="test_adapter",
+        category="test",
+        severity="routine",
+        title="Test Event",
+    )
+    payload = make_payload_from_event(event)
+
+    renderer = WebhookRenderer()
+    rendered = renderer.render(payload)
+
+    assert "source_event" in rendered
+    assert rendered["source_event"]["id"] == event.id
+    assert rendered["source_event"]["source"] == "test_adapter"
+
+
+def test_webhook_render_is_json_serializable():
+    """Rendered output is JSON-serializable (no datetime objects)."""
+    event = make_event(
+        source="test",
+        category="test",
+        severity="routine",
+        title="Test",
+    )
+    payload = make_payload_from_event(event)
+    payload.chunk_index = 1
+    payload.chunk_total = 3
+    payload.region = "Test Region"
+    payload.node_name = "Test-Node"
+
+    renderer = WebhookRenderer()
+    rendered = renderer.render(payload)
+
+    # Should not raise
+    json_str = json.dumps(rendered)
+    assert isinstance(json_str, str)
+    # Verify round-trip
+    parsed = json.loads(json_str)
+    assert parsed["message"] == payload.message
+
+
+def test_webhook_render_includes_optional_fields_when_set():
+    """Optional fields included when they have values."""
+    payload = NotificationPayload(
+        message="Test",
+        category="test_category",
+        severity="priority",
+        timestamp=time.time(),
+        event_type="battery_warning",
+        node_id="!abc123",
+        node_name="Test-Node",
+        region="Test Region",
+        chunk_index=2,
+        chunk_total=5,
+    )
+    renderer = WebhookRenderer()
+    rendered = renderer.render(payload)
+
+    assert rendered["category"] == "test_category"
+    assert rendered["event_type"] == "battery_warning"
+    assert rendered["node_id"] == "!abc123"
+    assert rendered["node_name"] == "Test-Node"
+    assert rendered["region"] == "Test Region"
+    assert rendered["chunk_index"] == 2
+    assert rendered["chunk_total"] == 5