refactor(benchmarks): own raster conformance captures

[thejustinwalsh]

Summary

• move finite MTSDF and Slug resource/capture lifecycles from live renderer modules into benchmark/targets/conformance/raster
• give both techniques the same direct warm conformance-session contract with borrowed-renderer and abort propagation
• move Slug source-outline, external-resource, role, affine, and projection-zoom proofs with their shared finite resource graph
• rewire conformance surfaces, runtime fallback, and every URL-loaded Slug quality probe to the target modules
• retain renderer modules for persistent live scenes and font/configuration infrastructure only

Verification

• mise exec -- pnpm benchmarks:check
• 60 files / 314 unit tests, including success, failure, abort, navigation disposal, and failed-capture state restoration
• all 19 isolated headless conformance scenarios
• retained comparison plus finite-capture/navigation recovery on WebGPU and forced WebGL2
• complete Slug role/affine/projection quality matrix on WebGPU and forced WebGL2 at DPR 1 and 2
• external Slug companion-resource parity on WebGPU and forced WebGL2
• mise exec -- pnpm docs:check: 0 errors, 0 warnings

Stack

Depends on #27.