fix: announce Christmas Eve, which OffDays lists but never returns

[eastagiletracker]

This PR proposes announcing Christmas Eve, which OffDays::HASHROCKET_HOLIDAYS lists but days_off never returns. We include this PR work along with a full history of your repo at https://eastagiletracker.com/projects/985. You can sign in with your GitHub ID to claim ownership of the project.

What was wrong

OffBot::OffDays::HASHROCKET_HOLIDAYS includes "Christmas Eve", and it has survived both prunings of that list (MLK/Presidents' Day in 2018, Good Friday in 2020). But the holidays gem defines no Christmas Eve for :us or :informal, and unlike New Year's Eve and Thanksgiving Friday it was never added to custom_holidays.yaml. So the name filter in days_off has nothing to match, and the Monday announcement silently skips it. Reproduced on current master (4ba013a) with Ruby 3.4.5:

$ bundle exec ruby -e 'require "./lib/offbot"; puts OffBot::MessageBuilder.build_message(message_start: "Happy Monday", from_date: Date.new(2025,12,22), to_date: Date.new(2026,1,5))'
Happy Monday:
Thursday, 25 Dec 2025: Christmas Day
Wednesday, 31 Dec 2025: New Year's Eve
Thursday, 01 Jan 2026: New Year's Day

The next miss would be the 21 Dec 2026 announcement, where Christmas Eve falls on a Thursday.

The change

• custom_holidays.yaml: define Christmas Eve (Dec 24, us, :informal) next to New Year's Eve, plus a matching entry in the file's tests: block. No observed: rule, so it reports the calendar date the same way the gem-provided holidays in this list do.
• lib/offbot/off_days.rb: mark the entry # in custom_holidays.yaml, like the other two custom ones.
• spec/offbot/off_days_spec.rb: the existing 2017 expectation now includes Sunday 24 Dec 2017, and a new example checks the week of 21 Dec 2026 returns Christmas Eve and Christmas Day.

After the change the same command prints Wednesday, 24 Dec 2025: Christmas Eve ahead of Christmas Day. bundle exec rspec spec was 3 examples, 0 failures before; with the new spec and without the YAML change it is 4 examples, 2 failures (both Christmas Eve expectations); with the change it is 4 examples, 0 failures (run several times, since the suite uses random order).

If Christmas Eve is no longer a Hashrocket day off, the other fix is to drop it from HASHROCKET_HOLIDAYS. Right now the list and the announcements disagree, and this PR goes with the list.

How this was managed

We imported this repo's 24 pull requests into a board at https://eastagiletracker.com/projects/985 and tracked this fix there as https://eastagiletracker.com/projects/985/stories/1123760.

If you'd rather not receive contributions like this, reply no-more-prs on this pull request and we won't open any further ones on your repositories.

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Lawrence W. Sinclair
CEO / East Agile
linkedin.com/in/lwsinclair/
eastagile.com