Split out from the full stage-2 move so every renamed file, including the two dissolving index pages, is recognized as a rename by git's similarity detection and is fully traceable via git log --follow. This commit is close to a pure `git mv`: file moves plus the mechanical link-rewrite pass; wiki/README.md and wiki/process/specs.md keep their pre-move content verbatim here (synthesized into their final form in the next commit) specifically so their rename is detected — a straight content rewrite alongside a move drops below git's rename-similarity threshold and the history link is lost. Defense: spec/wiki.md acceptance criterion 3 ("git log --follow reaches pre-migration history for every moved page") — verified for all 44 moved pages after this split, where the single-commit version left two as plain delete+add.