feat(sim): real zoom transitions on every ring edge, both directions

The cosmos→orbit, reef→abyss and abyss→cosmos transition clips were stale
leftovers from an earlier 5-scale ring, built against old/placeholder footage —
so those edges flashed placeholder frames mid-zoom. Only orbit-coast and
coast-reef had been rebuilt from the current real bases.

- build_pool_manifest.generate_media(): now rebuilds EVERY ring edge from the
  current real primary pool bases (the orbit-coast recipe applied uniformly),
  overwriting the stale clips, and bakes a reversed companion (<edge>.rev.mp4)
  per edge via an ffmpeg `reverse` pass.
- app.js: a `reversed` step (an ascending / zoom-OUT ring move) now plays the
  baked .rev clip instead of the forward zoom-in, so going up recedes from the
  current scale. Both directions are added to the in-memory preload set.

Media is gitignored (generated locally / on deploy); regenerated all 10 clips
locally. 269 passed, 2 skipped; node --check clean; clips serve 200.
Visual result to be verified by-eye by the operator.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

simulator/static/app.js

@@ -93,7 +93,11 @@ function mediaUrl(file) { return mediaBlobs[file] || ("/media/" + file); }
 function preloadList() {
   const files = new Set();
   for (const c of Object.values(clipsById)) if (c && c.base_file) files.add(c.base_file);
-  if (ring && ring.transitions) for (const t of ring.transitions) if (t && t.file) files.add(t.file);
+  // Each ring edge ships both directions: the forward (zoom-in) clip and its baked
+  // reverse (zoom-out) companion — cache both so up and down moves are instant.
+  if (ring && ring.transitions) for (const t of ring.transitions) {
+    if (t && t.file) { files.add(t.file); files.add(reverseFile(t.file)); }
+  }
   return [...files];
 }
 
@@ -110,7 +114,7 @@ function preloadOrder() {
       else if (s) add((clipsById[s.clip_id] || {}).base_file);
     }
   }
-  if (ring.transitions) for (const t of ring.transitions) add(t.file);
+  if (ring.transitions) for (const t of ring.transitions) { add(t.file); add(reverseFile(t.file)); }
   for (const f of preloadList()) add(f);   // sweep up anything not on the ring
   return ordered;
 }
@@ -515,11 +519,17 @@ function debounced() { clearTimeout(timer); timer = setTimeout(update, 80); }
 
 const FAST_BLEND_RATE = 2.5;   // playback speed for a collapsed fast-spin pass
 
-function playTransition(file, blended) {
+// The zoom-OUT companion of an edge clip: the baked `<edge>.rev.mp4` reverse. A
+// `reversed` step (an ascending / zoom-out ring move) plays this instead of the
+// forward zoom-in clip, so going up recedes from the current scale.
+function reverseFile(file) { return file.replace(/\.mp4$/, ".rev.mp4"); }
+
+function playTransition(file, blended, reversed) {
   // Play one zoom/warp transition clip start-to-finish, with the alteration
   // layers hidden. A `blended` (fast-spin) pass runs at FAST_BLEND_RATE so a
   // quick encoder spin lands fast instead of grinding through every morph.
-  // Resolves on 'ended' (or a safety timeout that scales with playback rate).
+  // Zoom-out moves (`reversed`) play the baked reverse clip. Resolves on 'ended'
+  // (or a safety timeout that scales with playback rate).
   return new Promise((resolve) => {
     overlay.style.opacity = "0";
     affectLayer.style.opacity = "0";
@@ -527,7 +537,7 @@ function playTransition(file, blended) {
     vid.style.filter = "none";
     vid.loop = false;
     vid.style.opacity = "1";
-    vid.src = mediaUrl(file);
+    vid.src = mediaUrl(reversed ? reverseFile(file) : file);
     vid.playbackRate = blended ? FAST_BLEND_RATE : 1;
     let done = false;
     const finish = () => {
@@ -556,7 +566,7 @@ async function advance(delta) {
     // A fast spin comes back collapsed to a single blended step (move.fast);
     // a slow spin chains one full transition per scale crossed.
     for (const step of move.steps) {
-      await playTransition(step.file, step.blended);
+      await playTransition(step.file, step.blended, step.reversed);
     }
     ringIndex = move.to_index;
     activeClipId = move.target_clip_id;   // the randomly-picked pool member to load