chat to video workflow stopped being a one-off experiment

spent the last few days finding out that the hard part was not getting one test video out. it was making the planning layer, review layer, and render layer stop disagreeing with each other. the spreadsheet, html review board, generated preview data, and remotion render could all drift if even one stale file survived. that kept showing up in very obvious ways: deleted visuals still rendering, backgrounds resetting when they should have continued, and the renderer making layout decisions that were never actually specified upstream.

the biggest workflow change was simplifying the visual system instead of trying to rescue the fancy version. the old overlay idea kept creating arbitrary placement, bad transparency handling, and too much room for the renderer to improvise. the cleaner rule is one background visual per beat. if something needs emphasis, change the background for that beat instead of floating another visual on top. that decision made the rules clearer, the review board easier to trust, and the render behavior easier to reason about.

also cleaned the repo up into a real scaffold instead of a single-session project dump. the session-specific media and tribe-specific render code got pulled out, the docs were rewritten as actual rules for a new agent, and the repo was republished as the generic system instead of one test case. separate but related pain: remotion / rspack kept failing under node 24 on this machine, not just here but in another project too. node 22 fixed it, so that is now the default.