docs: fix correctness issues found in review

Column identity follows the SummaryAgg's input schema (a Project renames
and drops the table); mark §6.1/§6.6 as #646 and per-family overlap as #592;
panes come from window composition (Pass 2); add IRate; three selection
shapes; current SummaryEstimate top-k output; time row of the definition
table; drop unchecked paper section numbers.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W7qG9aFyPij5uWsyAJCxDW

Author: zzylol