feat: Add previous workday mode to Mattermost extractor and enhance sync script

.opencode/commands/standup.md

@@ -24,9 +24,9 @@ Read:
 @knowledge/communication-rules.md
 @knowledge/agent-memory-rules.md
 
-Yesterday's log, if present:
+Previous workday Mattermost context, if present:
 
-!`y=$(date -v-1d +%F 2>/dev/null || python3 - <<'PY'\nfrom datetime import datetime, timedelta\nprint((datetime.now().astimezone() - timedelta(days=1)).strftime('%Y-%m-%d'))\nPY\n); if [ -f "ai/logs/$y.md" ]; then echo "$y"; cat "ai/logs/$y.md"; else echo "No log exists for yesterday."; fi`
+!`bash scripts/mattermost/sync.sh --previous-workday --today "$(date +%F)"`
 
 Today's log, if present:
 
@@ -44,7 +44,8 @@ Before drafting:
 
 - update workspace memory if the refreshed context introduced clear high-confidence project facts
 - prefer existing memory when the latest context is ambiguous
-- mention Jira IDs and approved titles when they map cleanly to yesterday's work
+- treat the previous workday Mattermost context as the source for the `Yesterday` section, even when the previous calendar day was a weekend, holiday, or OOO day
+- mention Jira IDs and approved titles when they map cleanly to previous-work context
 - prioritize story-based updates over side questions, memory refreshes, or manager-only context
 - if documentation or root cause updates directly support a story, roll them into that story's update instead of listing them separately
 - exclude items that are not directly tied to a story unless they are true blockers