Port the three asset-dependent examples (106 → 109)

[burinc]

Ports the three examples that were waiting on the asset files added in PR #4,
so those assets are now actually used. 106 → 109.

The three

tiled-drawing — tiles one patch of a texture atlas across the window,
with pattern, tint, scale and rotation selectable.

The substance is DrawTextureTiled, which is a helper defined inside the C
example rather than raylib API, so it's implemented here. Four cases (tile
larger than the area in both axes, larger in one, smaller in both), each
drawing partial tiles along its edges that crop the source proportionally so
a truncated tile shows less pattern rather than a squashed one.

Written as a pure function returning (source, dest) pairs instead of nested
draw loops, which is what makes it checkable: across all four cases the
tiles cover the destination area exactly, to within 1e-6, with every tile
inside it — verified at 500×400 (56 tiles), 528×396 (exact multiples, 48
tiles, no partials), 50×400, 500×40, 40×40, and scales 5.0 and 0.25 (4 and 800
tiles). The degenerate cases matter more than usual: the C's guard carries the
comment "Wanna see a infinite loop?!...just delete this line!". All four
inputs that trip it return empty.

palette-switch — eight bands drawn in near-black greys that a fragment
shader remaps through a palette. The colour on screen is never drawn by the
program; the red channel carries an index.

This is the example that finally exercises set-shader-value-ints!, whose GL
path was untested when I added it — the commit introducing it said so. It
works: 3-BIT RGB renders exactly black/red/green/blue/cyan/magenta/yellow/
white, which is only possible if all 24 ints reached the uniform in the right
order and grouping.

ascii-rendering — the scene rendered to an offscreen target, then
post-processed into ASCII glyphs. Nothing in the Clojure draws a glyph.

Verification

Shaders fail silently — LoadShader returns an id whether or not the GLSL
compiled — so these were checked by screenshot, not assertion. Before that,
each shader's uniforms were probed: nil for the vertex shader marshals to
NULL and raylib substitutes its default (the C passes 0 for the same
reason), palette resolves to location 1, and a deliberately absent uniform
returns -1. Both examples check their locations before use rather than
assuming success.

Gate: 138 namespaces, 0 lint errors, 69 warnings (unchanged backlog).

Also

• set-shader-value-vec2! — the namespace had float, vec3, vec4 and int
  helpers but no vec2, so a resolution uniform had nowhere to go.
• A texture-filter enum — set-texture-filter! previously took a bare
  int with no named constants.

Demos

ascii-rendering records well (44 frames, self-animating). tiled-drawing
and palette-switch come out at 2 distinct frames — the state does change
(10% and 6% of pixels differ end to end) but most keypresses don't land, the
known synthetic-input intermittency already documented in the manifest.
tiled-drawing's pattern and colour are chosen by clicking, which the
recorder can't deliver at all, so its timeline drives scale and rotation
instead. Both are candidates for a hand-recorded replacement.

Note on patterns.png

tiled-drawing depends on the one asset with no stated licence upstream,
flagged in resources/LICENSE.md. If you'd rather keep that directory
uniformly attributed, dropping the file costs exactly this one example.