Spin guard: derivative-work rule (AGENTS.md) + rationale (ai.md) — proactive external scan cites in commit msg; 2nd failed fix = STOP and research externally, never a 3rd guess

Project lesson cited (the 2026-08 web-box saga, 9 commits): browser sources are fixed canvases
per OBS convention — the 'gap' was a widget CSS glow, not a bug.

ai.md

@@ -14,6 +14,20 @@ Skip feature pitch, step-by-step implementation plans, pros/cons tables, and
 "potential pitfalls" sections unless the user explicitly asks for a plan first.
 A short diff-style summary beats a proposal document every time.
 
+## Derivative work (spin guard mandated in AGENTS.md)
+
+Nothing we build is novel — streaming/overlay/WebView2 problems were solved by
+OBS, CEV, and WPF ecosystems long before us. Two consequences:
+1. **Proactive:** new features start with a quick external scan, not head-first
+   design (citation goes in the commit message).
+2. **Objectively triggered spin guard:** a second failed fix for the same symptom
+   means STOP theorizing and research the established answer externally; there is
+   no unique bug in this repo that the wider ecosystem hasn't hit.
+This project's hard lesson: the web-source bounding saga (2026-08) burned 9
+commits rediscovering that a browser source is a *fixed canvas* — OBS keeps it at
+a stable page size, crops/hugs content via the box, and clips at the edge. The
+apparent "gap" that ended the saga was a widget's own CSS glow effect, not a bug.
+
 ## LAN infrastructure (192.168.50.x)
 
 All LAN credentials live in `CREDENTIALS.md` (gitignored). Server IPs and roles: