26.3 blocks, many bug fixes and improvements

• Add new blocks in 26.3.
• Add reading Minecraft 26.3 new format. 26.3's palette structure is different from 26.2, in that if a block's state is default, it is no longer stored.
• Double-column terrain storage. The old system had 16 tiles per column in TerrainExt.png. The new system has 32 columns, currently capping at 80 rows. This new architecture makes the textures not continue to grow the vertical dimension. New textures are added to the right-side of the image file. In this way it's a bit easier to visually check if previous Mineways texture files are comparable. The larger textures Minecraft has been introducing can now be stored, e.g., 32x32 or 64x64.
• 3-byte block storage. Mineways used 9 bits for the type, 7 bits for the block's data. 26.3 pushed the number of types over 511, forcing a new architecture. Now types have 12 bits (4096 types, plenty of room for future expansion) and 12 bits for data (likely enough). The downside is that block storage then takes 50 percent more room. But...
• Major bug fix: increase region export size. An exported region used to be tested to see if it would exceed 2^31 bytes of allocated data, a leftover from the Windows-32 days. Worse still, it would abort export if the full region selected was going to allocate space beyond this number of bytes. Mineways actually checks the volume and "lowers the sky" to the highest block in the region, which saves export memory. Also, it's the number of blocks, not blocks * bytes, that's more relevant with the current code. Long and short, removing this limitation and making sure the number of blocks is stored in a "long long" (64-bit) value, Mineways should now handle regions that are at least four times larger that before, if not larger.
• Strongly improved .schem export and import. More non-graphical attributes are read in and written out. Note-blocks' "instrument", decorated pot's "facing" and "cracked", sculk catalyst's "bloom", TNT's "unstable", piston's "sticky" and "short", bubble-column's "drag", and shelf's mysterious "side_chain" properties are now supported. An insane number of fixed due to the new Claude Code Opus 5.5. That said, things like wall and glass pane connections are maybe still problematic reading these in. Future work.
• Unused faces culling bug fixed; scripting in particular was not culling these well. Fewer hidden faces will be output now.
• Related, scripting was sometimes running before some table precomputes were being done on window creation. Fixed.
• Fix crash when using "export solid material colors", which accessed uninitialized UV data (that it didn't actually need).
• Be more careful about properly freeing image memory, out-of-memory conditions, file separators for any Mac version, TGA exceptions, etc. (Thanks to Will Breiler for #166. See his fork for a Mac-buildable version of Mineways.)
• Fix output count of smaller blocks. Was overcounting, based on number of boxes etc. for an object, e.g., each stairs gave a count of two, top and bottom.
• When an old terrain textures file is used, automatically fill in missing tiles with defaults and warn the user.
• Golem facing was incorrect, bleeding into other properties.
• Azaleas exported without textures could cause a crash. Fixed.
• Campfires could turn into soul campfires due to stale state held when "powered" is set. Fixed.
• Jigsaw orientation of west and north were swapped, and top face didn't rotate. Fixed.
• Lantern emission for soul lanterns was incorrectly at 15, now 10.
• In [Block Test World] make stone "supports" into glass, so textures are easier to examine. Other little fixes.
• Minor improvements to error messages, mineways.bat, etc.
• All terrain files updated, though, sadly, JG-RTX and LunaHD don't have 26.* block updates.
• TileMaker now at 3.30, ChannelMixer at 1.23.