Prove issue census pagination closure before reporting complete totals #472

🤖 Generated by the Agentic Engineer

Problem

The issue census requests pageInfo but its aggregation does not validate it. Missing pagination metadata or a stream claiming an unfetched next page can still report an empty census.

Reproduced offline against freshly fetched main with a valid control. Inspected guidance and repositories were not executed, and no inference or provider test was launched.

Acceptance criteria

Validate complete page/cursor shapes, a terminal final page, continuation consistency and issue inventory/count agreement; malformed/incomplete streams remain QUERY-UNKNOWN. Test actual shipped projection on complete empty and multipage controls. Size: S.

Part of #51. Related roadmap: #38.