Enhancement: Timeline-Based Relationship Discovery for Issue Sync

Context

We recently implemented a "Child-Triggered Parent Refresh" strategy to fix sync gaps where adding a sub-issue didn't update the parent's updatedAt timestamp. This works well for parent-child relationships.

Problem

The current logic only checks issue.parent. It does not handle:

1. Blocking Relationships: If Issue A blocks Issue B, and only A is updated/fetched, B's local file might remain stale (missing the "Blocked by A" entry) if GitHub doesn't bump B's updatedAt.
2. Edge Cases: Any other relationship change where the "other side" isn't automatically flagged as modified by GitHub.

Proposed Solution: Timeline-Based Discovery

Extend the post-processing logic in IssueSyncer.mjs to scan the timelineItems of all fetched issues.

1. Scan Events: Iterate through allIssues (the ones just pulled).
2. Filter Events: Look for relationship events (SUB_ISSUE_ADDED, BLOCKED_BY_ADDED, etc.) that occurred since the last sync.
3. Collect IDs: Extract the IDs of the related issues (event.subIssue.number, event.blockingIssue.number, etc.).
4. Force Update: Add these IDs to the forceUpdate set (merging with the existing issue.parent logic).

Implementation

Refactor the parentIdsToUpdate logic into a broader relatedIssuesToUpdate set.

const relatedIssuesToUpdate = new Set();

allIssues.forEach(issue => {
    // 1. Existing Parent Check
    if (issue.parent) {
        relatedIssuesToUpdate.add(issue.parent.number);
    }

    // 2. New Timeline Scan
    const relationshipEvents = issue.timelineItems?.nodes.filter(event => 
        ['SUB_ISSUE_ADDED_EVENT', 'BLOCKED_BY_ADDED_EVENT', /* ... all types */].includes(event.__typename) &&
        new Date(event.createdAt) > new Date(metadata.lastSync)
    );

    relationshipEvents?.forEach(event => {
        if (event.subIssue) relatedIssuesToUpdate.add(event.subIssue.number);
        if (event.parent) relatedIssuesToUpdate.add(event.parent.number);
        if (event.blockingIssue) relatedIssuesToUpdate.add(event.blockingIssue.number);
        if (event.blockedIssue) relatedIssuesToUpdate.add(event.blockedIssue.number);
    });
});

This ensures complete referential integrity for all relationship types.