Add an examples gallery to the docs

[BradyAJohnston]

Adds an Examples section to the docs: a Quarto grid listing of nine complete node trees, each linking through to a page with the script, a render, the interactive node tree and a link to the original.

Example	Ported from	Shows
Voxelize	Geometry Script tutorial	one >> chain, Set Material on generated geometry
Mesh to LEGO	Geometry Script Mesh to LEGO.py	CustomGeometryGroup, Mesh Boolean class methods
City Builder	Geometry Script tutorial	proximity selection, panels, frames
Repeat Grid	Geometry Script Repeat Grid.py	bounding-box arithmetic, .x/.y socket properties
Golf Ball	geonodes balls.py	map_range, a material built alongside the tree
Forest	geonodes forest.py	group variants from a Python list comprehension, helper functions for shaders
Gear Train	geonodes gears.py	Index Switch from Python lists, Python floats vs sockets in a loop
Explosion	geonodes explosion.py	simulation zone, field evaluation order
Arrow Field	geonodes arrows.py	vector arithmetic, .point.max(), instancer attributes in a material

The examples are rewritten as nodebpy code rather than translated line for line. Both source projects are GPL-3.0 like nodebpy.

How it fits together

• Each example is one script in docs/examples/code/. Its page pulls it in with {{< include >}} inside an executed {python} cell, so the code shown is the code that runs, and a hidden cell displays tree.
• docs/examples/render.py runs each example in its own bpy process, puts the tree on a staged object (Suzanne, an icosphere, a curve of roads or an empty mesh), frames the camera from the evaluated bounds and renders with Cycles on the CPU to a transparent PNG with a shadow catcher. Shots are configured per example in SHOTS.
• It is a Quarto pre-render step, and only re-renders examples whose script, shot or the render script changed (hashes in images/.hashes.json). The images are git-ignored; the docs workflow caches them.
• make examples runs it on its own.

Found along the way: s.AmbientOcclusion() comes out with samples=1 (the signature says 0, the RNA default) whereas Blender's own node starts at 16, so AO is effectively off unless samples is passed. The examples pass samples=16; the default needs fixing in the generator separately.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.30%. Comparing base (565b7c6) to head (bc85f80).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #255   +/-   ##
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  Coverage   98.30%   98.30%           
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  Files         101      101           
  Lines       30574    30574           
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  Hits        30056    30056           
  Misses        518      518           

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[codspeed]

Merging this PR will not alter performance

✅ 15 untouched benchmarks

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_{Comparing docs-examples (bc85f80) with main (565b7c6)}