Three PoC detail pages: incorporate discussion clarifications

Added bilingual review sections for the Umia decision-market, market-infrastructure buyback, and irreversible-switch cards. The additions distinguish concepts from implementations, correct single-metric limitations, and document a minimal contract responsibility boundary without rewriting the original essays.

PoC items 20-22: mark discussion work complete

Changed the three reviewed cards from planned to done after incorporating the discussion into their detail pages. Prepared the complete request branch, including the new daily history file, for commit and push.

PoC sidebar: show completed items in black

Updated the generated navigation entries for items 20–22 from the blue important state to the black done state. Applied the status consistently across the static PoC index and topic-page sidebars.