The System Overview ASCII diagram had inconsistent box widths:
- Entry Points box bottom border was 73 chars instead of 71
This caused the docs-site-checks CI to fail on every docs-only PR
due to pre-existing errors in the diagram.
Fix: normalize Entry Points bottom border to 71 characters,
matching the top border width.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>