Fixes the throughput metrics script and introduces new visibility into backlog bottlenecks and priority distribution.
### Changes
- **Throughput Fixes**: Resolved a `ReferenceError` where `isMaintainer` was not correctly scoped, fixed a malformed license header, and added a new metric for `issue_arrival_rate_per_day` to enable growth-vs-closure analysis.
- **Backlog Bottlenecks**: Introduced `bottlenecks.ts` to identify "Zombie" issues (no activity > 30 days) and "Hot" issues (high activity).
- **Priority Distribution**: Introduced `priority_distribution.ts` to track the count of open issues by priority level (P0-P3).
### Impact
These metrics will provide the necessary data to confirm if the repository is experiencing systemic backlog growth (Arrival Rate > Throughput) and help identify which segments of the backlog require urgent triage.
Christian Gunderman