Fix animgallery rendering bugs and mitigate AI-upscale frame flicker

- writeGIF now pads every frame to one shared canvas instead of
  writing each at its own (possibly storage-cropped) size - GIF
  disposal rules were showing a previous frame's stale pixels through
  the uncovered border of a smaller frame, bleeding content between
  frames in the gallery.
- decodeFrames/decodeViewFrames/decodeAnimationFrames now always hand
  bitmap.DecodeReferenced a zero buffer instead of the previous
  frame/block's real pixels. The game's actual RSD8 decoder treats a
  "skip" run as literal zero, with no mechanism to carry a reference
  frame's pixels forward (confirmed against Night Dive's published
  source), and hacked's own multi-block Bitmap preview decodes the
  same way. The previous behavior ghosted a previous frame's stale
  content into the current frame's skip-run regions, in both the
  gallery and the AI upscaler's source input.
- index.html now shows a labeled per-frame filmstrip next to each
  animated GIF, and a base-vs-this-build side-by-side comparison for
  every resource a mod overrides.
- Gallery GIFs play back at a third of real speed by default, for
  easier frame-by-frame review.
- modding/mods/*/bitmaps/*.json gains considerPreviousFrames: a
  per-resource list that runs a temporal-consistency pass (median
  across the animation's own frames) on independently-upscaled frames
  to reduce per-frame AI flicker. Applied to 0x7B1 in upscale_medbot.
- Drop the rebecca-test example mod.

modding/mods/rebecca-test/messages/mail-026.json

@@ -1,7 +0,0 @@
-{
-    "type": "Mails",
-    "index": 26,
-    "sender": "Rebecca Lansing1",
-    "title": "Rebecca-001",
-    "verboseTextFile": "mail-026.txt"
-}

modding/mods/rebecca-test/messages/mail-026.txt

@@ -1 +0,0 @@
-Listen to me very carefully HACKER. Something has gone terribly wrong on Citadel station. You might be the last survivor. Communications are being jammed. We know that something on board is attempting to harm humanity. The mining laser is being charged for a possible strike against Earth populations. On your level is the office of a Dr. D'Arcy, who may know something about the laser.  The office is located near the central hub, on a balcony, with the medical icon clearly visible. When the laser is destroyed, you will have to reach the bridge and stop whatever is responsible for the catastrophe. We believe that the biological labs and security systems have gone haywire, so be careful. If you pull this off, we will be able to get you out alive. Good luck.

modding/mods/upscale_medbot/bitmaps/medbot.json

@@ -22,5 +22,6 @@
     "0x7B6",
     "0x7B7",
     "0x84C"
-  ]
+  ],
+  "considerPreviousFrames": ["0x7B1"]
 }