release: v0.1.8 — scene graph fixes + deps cascade

[kolkov]

Summary

5 bug fixes (merged PRs #26-29, #31) + ecosystem deps cascade.

Fixed

• Duplicate ambient lights — double ambient contribution from redundant scan (#26)
• Non-indexed geometry — DrawIndexed called unconditionally, now branches to Draw (#31)
• LookAt parallel up — NaN/Inf when camera looks along up vector (#29)
• Stale matrices — public field mutation bypassed dirty flags (#27)
• Directional light + scale — quaternion extracted from scaled world matrix (#28)

Changed

• deps: wgpu v0.31.2, gputypes v0.5.2
• examples: gogpu v0.52.1, gg v0.52.2, gpucontext v0.27.0, ui v0.1.53

Test plan

• go build ./... — pass (Windows, Linux, macOS)
• go test ./... — 523 test runs, 4/4 packages
• golangci-lint run — 0 issues
• All 3 examples build
• All PRs individually CI-green + code reviewed + approved

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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