refactor(benchmarks): expose canonical font asset flow

[thejustinwalsh]

Summary

• add a workload-facing font-asset contract and selected-technique adapter
• move source-font selection, baked fixture transport, gzip/SHA-256 authentication, public FontLoader runtime fallback, raster requests, progress, and delivery metrics out of renderer-owned modules
• preserve literal Bitmap/MTSDF/Slug dynamic imports and the published lazy @pmndrs/text/runtime-bake boundary
• retain live renderer lifecycle, GPU configuration, resource statistics, and compatibility delegates inside renderer/
• reject direct font-baker or Wasm URL reach-through from workload asset code

Verification

• mise exec -- pnpm benchmarks:check — 56 files, 310 tests; lint, formatting, strict types, size budgets, and production build passed
• production build retained separate font-assets, Bitmap, MTSDF, and Slug chunks with no ineffective dynamic-import warning
• mise exec -- pnpm benchmarks:check:react-doctor — no issues
• mise exec -- pnpm benchmarks:test:presentation — all 42 sequential workload cells passed with visible pixels and one renderer; timed demos passed at 60.02 FPS WebGPU and 60.47 FPS WebGL2 and returned to Off-axis / 3D
• headless conformance — all 19 scenarios passed
• external raster proof — deterministic WebGPU and WebGL2 frames passed through the runtime loader path
• mise exec -- pnpm docs:check — 0 errors, 0 warnings

Stacked on #24.