refactor: organise assets, tidy player.gd, unbreak fresh import

Assets grouped by role, within the constraint that FBX materials resolve
their textures by path relative to the FBX itself (verified by forcing a
reimport and reading back the albedo paths):

  assets/level/   scene.fbx + Level1_v1.fbx + the platform maps they look
                  up as siblings
  assets/logos/   the three attribution logos
  assets/         chara_red.fbx, background.fbx — these reach up into
                  ../sourceimages and so cannot move
  sourcefiles/    scene.blend, behind a .gdignore

The .blend move is a bug fix, not tidying. Godot hands every importable
.blend to a headless Blender, and that call never returns on this project
— a fresh clone stalls on first import, and the machine still had orphaned
Blender processes from an earlier attempt. Nothing loads the .blend: the
level geometry is baked into level_1.tscn.

player.gd: spell out ct/bt/d/ix/a, type the physics step, group the
members, and point the blue skin at sourceimages/low_blue_mat_* — the same
files assets/Chara_blue/ was a byte-identical copy of.

Co-Authored-By: Claude Opus 5 <[email protected]>

assets/level/platforms_standardSurface3_Metallic_Utility - Raw.1001.png.import

@@ -0,0 +1,40 @@
+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://deegjbiilo4qh"
+path="res://.godot/imported/platforms_standardSurface3_Metallic_Utility - Raw.1001.png-8ae6b39f540d1f7687eb0502425b6574.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://assets/level/platforms_standardSurface3_Metallic_Utility - Raw.1001.png"
+dest_files=["res://.godot/imported/platforms_standardSurface3_Metallic_Utility - Raw.1001.png-8ae6b39f540d1f7687eb0502425b6574.ctex"]
+
+[params]
+
+compress/mode=0
+compress/high_quality=false
+compress/lossy_quality=0.7
+compress/uastc_level=0
+compress/rdo_quality_loss=0.0
+compress/hdr_compression=1
+compress/normal_map=0
+compress/channel_pack=0
+mipmaps/generate=false
+mipmaps/limit=-1
+roughness/mode=0
+roughness/src_normal=""
+process/channel_remap/red=0
+process/channel_remap/green=1
+process/channel_remap/blue=2
+process/channel_remap/alpha=3
+process/fix_alpha_border=true
+process/premult_alpha=false
+process/normal_map_invert_y=false
+process/hdr_as_srgb=false
+process/hdr_clamp_exposure=false
+process/size_limit=0
+detect_3d/compress_to=1