feat: Add invite compressor and compressed header display

- Add InviteCompressor for terminal-friendly calendar invite summaries
- Add test fixtures for large group invite and cancellation emails
- Compress To/CC headers to single line with '... (+N more)' truncation
- Add 'h' keybinding to toggle between compressed and full headers
- EnvelopeHeader now shows first 2 recipients by default

tests/test_invite_compressor.py

@@ -0,0 +1,183 @@
+"""Tests for calendar invite compression."""
+
+import pytest
+from pathlib import Path
+
+from src.mail.invite_compressor import InviteCompressor, compress_invite
+from src.mail.utils.calendar_parser import (
+    parse_calendar_from_raw_message,
+    is_cancelled_event,
+    is_event_request,
+)
+from src.mail.notification_detector import is_calendar_email
+
+
+class TestInviteDetection:
+    """Test detection of calendar invite emails."""
+
+    def test_detect_large_group_invite(self):
+        """Test detection of large group meeting invite."""
+        fixture_path = Path(
+            "tests/fixtures/test_mailbox/INBOX/cur/17051227-large-group-invite.test:2,S"
+        )
+        assert fixture_path.exists(), f"Fixture not found: {fixture_path}"
+
+        with open(fixture_path, "r") as f:
+            raw_message = f.read()
+
+        # Create envelope from message
+        envelope = {
+            "from": {"addr": "product.dev@example.com", "name": "Product Development"},
+            "subject": "Project Kickoff Meeting",
+            "date": "2025-12-19T21:42:58+00:00",
+        }
+
+        # Should be detected as calendar email
+        assert is_calendar_email(envelope) is True
+
+        # Parse the ICS
+        event = parse_calendar_from_raw_message(raw_message)
+        assert event is not None
+        assert event.method == "REQUEST"
+        assert is_event_request(event) is True
+        assert event.summary == "Project Kickoff Meeting"
+        assert len(event.attendees) >= 20  # Large group
+
+    def test_detect_cancellation(self):
+        """Test detection of meeting cancellation."""
+        fixture_path = Path(
+            "tests/fixtures/test_mailbox/INBOX/cur/17051228-cancellation.test:2,S"
+        )
+        assert fixture_path.exists(), f"Fixture not found: {fixture_path}"
+
+        with open(fixture_path, "r") as f:
+            raw_message = f.read()
+
+        envelope = {
+            "from": {"addr": "cody.marshall@example.com", "name": "Marshall, Cody"},
+            "subject": "Canceled: Technical Refinement",
+            "date": "2025-12-19T19:12:46+00:00",
+        }
+
+        # Should be detected as calendar email
+        assert is_calendar_email(envelope) is True
+
+        # Parse the ICS
+        event = parse_calendar_from_raw_message(raw_message)
+        assert event is not None
+        assert event.method == "CANCEL"
+        assert is_cancelled_event(event) is True
+        assert event.status == "CANCELLED"
+
+
+class TestInviteCompression:
+    """Test compression of calendar invite content."""
+
+    def test_compress_large_group_invite(self):
+        """Test compression of large group meeting invite."""
+        fixture_path = Path(
+            "tests/fixtures/test_mailbox/INBOX/cur/17051227-large-group-invite.test:2,S"
+        )
+        with open(fixture_path, "r") as f:
+            raw_message = f.read()
+
+        envelope = {
+            "from": {"addr": "product.dev@example.com", "name": "Product Development"},
+            "subject": "Project Kickoff Meeting",
+            "date": "2025-12-19T21:42:58+00:00",
+        }
+
+        compressor = InviteCompressor(mode="summary")
+        compressed, event = compressor.compress(raw_message, envelope)
+
+        assert event is not None
+        assert "MEETING INVITE" in compressed
+        assert "Project Kickoff Meeting" in compressed
+        # Should show compressed attendee list
+        assert "more)" in compressed  # Truncated attendee list
+        # Should show action hints for REQUEST
+        assert "Accept" in compressed
+
+    def test_compress_cancellation(self):
+        """Test compression of meeting cancellation."""
+        fixture_path = Path(
+            "tests/fixtures/test_mailbox/INBOX/cur/17051228-cancellation.test:2,S"
+        )
+        with open(fixture_path, "r") as f:
+            raw_message = f.read()
+
+        envelope = {
+            "from": {"addr": "cody.marshall@example.com", "name": "Marshall, Cody"},
+            "subject": "Canceled: Technical Refinement",
+            "date": "2025-12-19T19:12:46+00:00",
+        }
+
+        compressor = InviteCompressor(mode="summary")
+        compressed, event = compressor.compress(raw_message, envelope)
+
+        assert event is not None
+        assert "CANCELLED" in compressed
+        # Title should be strikethrough (without the Canceled: prefix)
+        assert "~~Technical Refinement~~" in compressed
+        # Should NOT show action hints for cancelled meetings
+        assert "Accept" not in compressed
+
+    def test_attendee_compression(self):
+        """Test attendee list compression."""
+        compressor = InviteCompressor()
+
+        # Test with few attendees
+        attendees = ["Alice <alice@example.com>", "Bob <bob@example.com>"]
+        result = compressor._compress_attendees(attendees)
+        assert result == "Alice, Bob"
+
+        # Test with many attendees
+        many_attendees = [
+            "Alice <alice@example.com>",
+            "Bob <bob@example.com>",
+            "Carol <carol@example.com>",
+            "Dave <dave@example.com>",
+            "Eve <eve@example.com>",
+        ]
+        result = compressor._compress_attendees(many_attendees, max_shown=3)
+        assert "Alice" in result
+        assert "Bob" in result
+        assert "Carol" in result
+        assert "(+2 more)" in result
+
+    def test_compress_off_mode(self):
+        """Test that compression can be disabled."""
+        fixture_path = Path(
+            "tests/fixtures/test_mailbox/INBOX/cur/17051227-large-group-invite.test:2,S"
+        )
+        with open(fixture_path, "r") as f:
+            raw_message = f.read()
+
+        envelope = {
+            "from": {"addr": "product.dev@example.com"},
+            "subject": "Project Kickoff Meeting",
+        }
+
+        compressor = InviteCompressor(mode="off")
+        assert compressor.should_compress(envelope) is False
+
+        compressed, event = compressor.compress(raw_message, envelope)
+        assert compressed == ""
+        assert event is None
+
+    def test_convenience_function(self):
+        """Test the compress_invite convenience function."""
+        fixture_path = Path(
+            "tests/fixtures/test_mailbox/INBOX/cur/17051227-large-group-invite.test:2,S"
+        )
+        with open(fixture_path, "r") as f:
+            raw_message = f.read()
+
+        envelope = {
+            "from": {"addr": "product.dev@example.com"},
+            "subject": "Project Kickoff Meeting",
+        }
+
+        compressed, event = compress_invite(raw_message, envelope)
+        assert event is not None
+        assert "Project Kickoff Meeting" in compressed