## Approach
The orchestrator polling loop previously made individual API calls for each PR's
state, CI status, and review decision - 3 separate calls per PR per poll.
With multiple PRs being monitored, this quickly exhausted GitHub's 5,000-point
hourly rate limit.
This PR implements GraphQL batching using aliases, which allows fetching data
for up to 25 PRs in a single GraphQL query. Additionally, a 2-Guard ETag
strategy is used to skip queries entirely when nothing has changed.
## Implementation
### GraphQL Batching
- `generateBatchQuery()` creates a single GraphQL query with unique aliases (pr0, pr1, pr2...)
- Each PR gets the same set of fields: state, CI status, review decision, mergeability
- Uses inline fragments for union types (CheckRun/StatusContext)
- Variable types: String! for owner/repo, Int! for PR numbers
### 2-Guard ETag Strategy
Before running expensive GraphQL queries, two lightweight REST ETag checks detect if
anything changed:
**Guard 1 (PR List ETag):**
- Checks `/repos/{owner}/{repo}/pulls` with If-None-Match header
- Returns 304 if no changes → skips GraphQL (0 points)
- Detects: New commits, title/body edits, labels, reviews, state changes
**Guard 2 (Commit Status ETag):**
- Checks `/repos/{owner}/{repo}/commits/{sha}/status` per cached PR
- Returns 304 if no changes → skips GraphQL (0 points)
- Detects: CI status transitions (failing → passing, passing → failing, etc.)
### Caching
- LRU caches for PR metadata (max 200 entries), ETags (100/500 entries)
- Cache misses trigger individual API fallback via lifecycle-manager
- No placeholder caching on errors - allows proper fallback behavior
## Impact
- **API reduction:** ~88% fewer REST calls (216 vs 1,800 calls/hour for 5 PRs)
- **GraphQL efficiency:** Batch query fetches 25 PRs for ~40 points vs ~400 for individual calls
- **Polling interval:** Still 30s, but most polls return cached data (0 cost)
- **Fallback:** Individual SCM calls still work for edge cases (permissions, cache misses)
## Testing
- Unit tests for query generation and parsing helpers
- Integration tests for real GraphQL API calls (skipped by default)
- Covers batch failures, partial success, empty arrays, edge cases
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