nx_skill_video.nx

nx_skill_video.nx -- LIB: WHO you learn a technique from is the learner's choice, not ours. For any skill the coach teaches, there may be several ways to watch it done: a PROFESSIONAL source, an AMATEUR one (often better -- a home cook's kitchen looks like yours), or a specific CHEF the learner already follows. This registry holds those sources per skill, keeps the chefs a person follows, and answers the question that actually gets asked: "has the cook I like already covered this?" THAT QUESTION IS A TRI-STATE, ON PURPOSE. sv_chef_covers returns -1 for a chef we have never heard of, 0 for a chef we know who has not covered this skill, and 1 for covered. Collapsing the first two into "no" would tell someone their favourite chef has not made the video when the truth is we never indexed them -- and that wrong answer is exactly what would send a pointless request to a chef who already has one. LINK ROT IS THE SAME PROBLEM AS THE RECIPE. A technique video is a citation like any other, so this reuses ms_is_archived from nx_meal_source rather than growing a second archive predicate: a source renders as preserved ONLY when its bytes actually come back out of the WARC. Schema (prefix passed in, e.g. knowledge/store/skillvid-): svid:ids -> TAB list of video ids svid:<vid> -> skill <t> title <t> creator <t> kind <t> url <t> licence <t> seconds <t> chef-id svid:skill:<sid> -> TAB list of video ids teaching that skill chef:ids -> TAB list of chef ids chef:<cid> -> display name <t> handle <t> home url follow:<unit> -> TAB list of chef ids this unit follows license_tier: ORIGINAL No hw writes (Rule 26).