Change deploy notifications to daily version bumps (#24)

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.

.github/workflows/deploy-notify.yml

@@ -1,8 +1,14 @@
-name: Deploy Notification
+name: Daily Version Bump
 
 on:
-  push:
-    branches: [main]
+  schedule:
+    # 6pm ET (EDT = 22:00 UTC, EST = 23:00 UTC)
+    - cron: "0 22 * * *"
+    - cron: "0 23 * * *"
+  workflow_dispatch: {}
+
+permissions:
+  contents: write
 
 jobs:
   notify:
@@ -10,26 +16,69 @@ jobs:
     steps:
       - uses: actions/checkout@v4
         with:
-          fetch-depth: 2
+          fetch-depth: 0
+          fetch-tags: true
 
-      - name: Extract version info from commit
-        id: info
+      - name: DST guard
+        id: dst
         run: |
-          MSG=$(git log -1 --pretty=%s)
-          echo "message=$MSG" >> "$GITHUB_OUTPUT"
-          # Count merge commits on main as version number
-          COUNT=$(git rev-list --count HEAD)
-          echo "count=$COUNT" >> "$GITHUB_OUTPUT"
+          HOUR=$(TZ=America/New_York date +%H)
+          if [ "$HOUR" != "18" ]; then
+            echo "ET hour is $HOUR, not 18 — wrong DST rule fired"
+            echo "skip=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "skip=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Check for changes since last version tag
+        if: steps.dst.outputs.skip != 'true'
+        id: changes
+        run: |
+          LAST_TAG=$(git tag -l 'v*' --sort=-v:refname | head -1)
+          if [ -z "$LAST_TAG" ]; then
+            echo "No previous version tag — using full history"
+            COMMITS=$(git log --oneline --pretty=format:"%s")
+          else
+            COMMITS=$(git log "$LAST_TAG"..HEAD --oneline --pretty=format:"%s")
+          fi
+
+          if [ -z "$COMMITS" ]; then
+            echo "No new commits since $LAST_TAG"
+            echo "has_changes=false" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+
+          echo "has_changes=true" >> "$GITHUB_OUTPUT"
+
+          # Build bullet list from commit messages, skip merge commits
+          BULLET_LIST=$(echo "$COMMITS" | grep -v "^Merge" | sed 's/^/• /')
+          {
+            echo "bullets<<ENDOFBULLETS"
+            echo "$BULLET_LIST"
+            echo "ENDOFBULLETS"
+          } >> "$GITHUB_OUTPUT"
+
+          # Date-based version
+          VERSION="v$(date +%Y.%m.%d)"
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+
+      - name: Create version tag
+        if: steps.dst.outputs.skip != 'true' && steps.changes.outputs.has_changes == 'true'
+        run: |
+          git tag ${{ steps.changes.outputs.version }}
+          git push origin ${{ steps.changes.outputs.version }}
 
       - name: Post to Slack
+        if: steps.dst.outputs.skip != 'true' && steps.changes.outputs.has_changes == 'true'
         env:
           SLACK_BOT_TOKEN: ${{ secrets.SLACK_BOT_TOKEN }}
           SLACK_CHANNEL_ID: ${{ secrets.SLACK_CHANNEL_ID }}
+          VERSION: ${{ steps.changes.outputs.version }}
+          BULLETS: ${{ steps.changes.outputs.bullets }}
         run: |
+          TEXT=$(printf ":rocket: *%s deployed*\n\n%s" "$VERSION" "$BULLETS")
           curl -s -X POST https://slack.com/api/chat.postMessage \
             -H "Authorization: Bearer $SLACK_BOT_TOKEN" \
             -H "Content-Type: application/json" \
-            -d "$(jq -n \
-              --arg channel "$SLACK_CHANNEL_ID" \
-              --arg text ":rocket: *Deployed to production* — ${{ steps.info.outputs.message }}" \
+            -d "$(jq -n --arg channel "$SLACK_CHANNEL_ID" --arg text "$TEXT" \
               '{channel: $channel, text: $text}')"