Timecode: nominal fps + proper drop-frame detection, shell-safe plan output; streams never VFR-re-encoded; gap list in the sidecar; docs

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

bin/normalize-sweep.sh

@@ -61,7 +61,9 @@ probe() {
                med=d[int(n/2)]; if (med<=0) { print "cfr"; exit }
                bad=0; for(i=0;i<n;i++){ x=d[i]-med; if(x<0)x=-x; if (x > med*0.25) bad++ }
                print (bad > n*0.02) ? "vfr" : "cfr" }')
-  [[ $vfr == vfr ]] && { echo "encode vfr"; return; }
+  # streams: gaps from dropped frames are legitimate and re-encoding a 3 h file is hours of CPU — never VFR-encode
+  # them (the timecode sidecar lists the gaps instead). Clips (short, often genuinely VFR) still get CFR.
+  if [[ $vfr == vfr && $f != "$ROOT/streams/"* ]]; then echo "encode vfr"; return; fi
   local moov mdat; moov=$(grep -o '[0-9]*:moov' <<<"$head" | cut -d: -f1 | head -1); mdat=$(grep -o '[0-9]*:mdat' <<<"$head" | cut -d: -f1 | head -1)
   if [[ -z $moov || ( -n $mdat && $mdat -lt $moov ) ]]; then echo "remux index-last"; return; fi
   echo "ok"