fix: resolve 147 markdownlint errors across 5 meta-docs + investigation + technique

Add language specifiers (text/python/yaml/solidity/ebnf/sql/typescript) to
unlabeled fenced code blocks, blank lines around fences and lists, wrap bare
URLs in angle brackets, replace emphasis-as-heading with proper h3.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: iZonex