Reworks the daily version bump workflow to:
- Pull merged PR titles via gh CLI instead of raw commit messages
- Post a polished, non-technical channel message with a link to the
changelog canvas
- Prepend the new version entry to the Slack canvas via canvases.edit
API so the canvas stays in sync automatically
Channel message format:
"After-Hours Scheduler has been updated to vXXXX.XX.XX
Here's a brief summary of what changed:
• ...
Click here to read the full changelog"
Replaces per-push notifications with a daily 6pm ET cron job that
batches all commits since the last version tag into a single Slack
message. Tags main with a date-based version (v2026.05.01) so there
is at most one version bump per day. Includes DST guard matching the
pattern used by the other scheduled Lambdas.
