Importing cancellation of a single event in a series deletes series, leaves single event

Describe the bug
Given a recurring event, if I import an .ics file that represents the cancellation for a specific instance (recurrence), then then khal deletes the whole series and leaves only one event in place, namely the one that was cancelled, except it's not cancelled. Effectively, khal import does the exact opposite of what it should do.

To Reproduce
Steps to reproduce the behavior:

0. Unpack khal.zip

1. Import the included invitation;

2. Confirm that a new daily event "Test2" exists:

    % khal list 2026-04-20 2d
    Monday, 2026-04-20
    13:00-13:40 Test2 ⟳
    Tuesday, 2026-04-21
    13:00-13:40 Test2 ⟳
   

3. Import the included cancellation, which is a METHOD:CANCEL with RECURRENCE-ID:20260421T130000, i.e. cancelling the event instance on 2026-04-21;

4. Confirm that the cancelled event on Tuesday is actually still there (albeit cancelled), but the other events in the recurrence are gone:

    % khal list 2026-04-20 2d
    Tuesday, 2026-04-21
    CANCELLED 13:00-13:40 Test2 ⟳
   

OS, version, khal version and how you installed it:

0.14.0 from PyPi, Python 3.13.12, Debian unstable, amd64, empty config

click==8.3.2
click-log==0.4.0
configobj==5.0.9
icalendar==7.0.3
khal==0.14.0
python-dateutil==2.9.0.post0
pytz==2026.1.post1
pyxdg==0.28
six==1.17.0
tzdata==2026.1
tzlocal==5.3.1
urwid==4.0.0
wcwidth==0.6.0

Start with the khal import entry point and reproduce the behavior using the attached khal.zip, first importing the recurring “Test2” invitation and then its METHOD:CANCEL with RECURRENCE-ID:20260421T130000. Done means the cancellation removes only the 2026-04-21 instance while the other events in the daily series remain.