Improve OpenIsopix MVP readiness

[starsaintf]

Summary

Builds on the existing isometric tilemap work from PR #3 and fills in the remaining issue #1 readiness gaps I could verify locally:

• route mouse/controller bindings through the declared InputMap actions for place/remove interactions
• convert screen coordinates through the active camera canvas transform so picking/highlight positions track panning and zoom correctly
• use the camera focus world position for chunk loading instead of a rough camera-position division
• render block textures through BlockType.get_current_frame() so animated/custom block types can drive frames
• cap block/highlight z-index values inside Godot's CanvasItem range, fixing the startup runtime error from the cursor highlight
• clean stale docs for the removed QUERY/Torch paths and add a small source regression check

Validation

• python tests\source_check.py
• python -m py_compile tests\source_check.py
• rg -n "QUERY|Torch|camera\.position\.x / 100|<<<<<<<|>>>>>>>|z_index = 10000" scripts docs CONTROLS.md project.godot scenes returned no matches
• Godot_v4.5.1-stable_win64_console.exe --headless --path . --import --verbose
• Godot_v4.5.1-stable_win64_console.exe --headless --path . --scene res://scenes/Main.tscn --quit-after 5 --verbose

Closes #1