Summary

Add examples/series-webgl-bar-uniform/ — demonstrates using fc.webglUniform() to pass global parameters to custom fragment shaders.

Bars are rendered with horizontal stripes where the stripe width is controlled by a uniform. Teaches the uniform binding pattern in isolation.

Motivated by #1894 — user's solution used fc.webglUniform() for hatch spacing with no existing example to reference.

Key APIs demonstrated:

• fc.webglUniform().data(value)
• program.buffers().uniform('uStripeWidth', uniform)
• program.fragmentShader().appendHeader('uniform highp float uStripeWidth;')

Test plan

• npm run lint — clean
• Visual verification in browser — bars render with horizontal stripe pattern
• Example follows existing pattern
• Changeset included