refactor(benchmarks): extract persistent viewport controllers

[thejustinwalsh]

Summary

• move Bitmap, MTSDF, and Slug persistent live-text viewport controllers from the route coordinator into surfaces/benchmark
• colocate warm update queues, host leases, loading/error chrome, telemetry attributes, and shared viewport contracts with their rendered surfaces
• preserve literal dynamic renderer imports and add a boundary test requiring every static renderer reference to remain type-only
• reduce app.tsx from 2,647 to 1,661 lines while leaving route orchestration and the retained comparison viewport in place

Evidence

• mise exec -- pnpm benchmarks:check
  • 53 test files / 301 tests before the boundary fixture; focused boundary adds 3 passing cases
  • TypeScript, OXLint, Oxfmt, scripts, size gates, and production build passed
• production build review
  • separate bitmap-text, mtsdf-text, and slug-text chunks retained
  • no ineffective-dynamic-import warnings after converting renderer references to explicit import type
• mise exec -- pnpm benchmarks:check:react-doctor
  • React Doctor 0.7.2 reported no issues
• mise exec -- pnpm --filter @pmndrs/text-benchmarks test:presentation-workloads
  • all 42 retained-scene cells rendered visible pixels across all techniques and both backends
  • exactly one renderer remained alive per lane
• mise exec -- pnpm --filter @pmndrs/text-benchmarks test:presentation-demo
  • both 60-second demos traversed Advanced Shaping and the complete authored workload sequence
  • both returned to Off-axis / 3D with one renderer
  • Icon Grid measured 60.02 FPS on WebGPU and 60.36 FPS on forced WebGL2
• mise exec -- pnpm docs:check
  • OKF v0.2: 0 errors, 0 warnings

Boundaries

• Persistent renderer/canvas/RAF/GPU timer ownership remains in the route host.
• The extracted controllers retain the existing public data/test-id probe contract exactly.
• No renderer implementation or package API changed.

Stacked on #22.