refactor(benchmarks): isolate canonical workload examples

[thejustinwalsh]

Summary

• move every retained Presentation workload's authored content and public Text construction into a dedicated apps/benchmarks/src/workloads/ example module
• add an exhaustive workload registry for camera, content-width, warm-update, and Icon Grid suspension policy while keeping renderer, canvas, RAF, telemetry, font delivery, and disposal in the persistent host adapter
• isolate product, measurement, and conformance targets behind a lazy application-safe registry so direct font-baker and Wasm URL modules load only after an explicit low-level target selection
• remove the Paragraph Stress presentation RAF allocation by reusing caller-owned motion state

Architecture

The seven comparison workloads now read as package-consumer examples: Text Ladder, Zoom Text, Icon Grid, Off-axis 3D, Dynamic Layout, Paragraph Stress, and Paint & Effects each visibly construct public @pmndrs/text Text objects in their own module. renderer/comparison-workload.ts remains the generic retained-scene adapter and contains no new Text(...) calls.

Low-level targets now live under benchmark/targets/product, measurement, and conformance. benchmark/targets.ts is a two-line lazy facade. A deterministic boundary test allowlists direct font-baker/Wasm imports to one low-level dependency adapter and resolves every registered target ID.

This changes benchmark application structure only. It does not add a public package API, change runtime/baker/Wasm artifacts, or change renderer ownership.

Verification

• pnpm benchmarks:check — 271 unit tests, lint, formatting, production build, and exact package-size checks passed
• pnpm --filter @pmndrs/text-benchmarks test — complete size, autoresearch, bidi/CJK contract, unit, headless conformance, and packed-consumer suite passed
• pnpm benchmarks:check:react-doctor — no issues found
• pnpm docs:check — zero conformance, producer-profile, or warning findings
• sequential Presentation workload matrix — all seven workloads rendered visible DPR-2 framebuffer pixels with one renderer for Bitmap, MTSDF, and Slug on WebGPU and forced WebGL2
• timed Presentation demo — complete authored sequence passed on WebGPU and forced WebGL2, including Advanced Shaping, both Icon Grid entries, focused-control Space capture, and final Off-axis 3D frame; observed Icon Grid rates were 59.8 FPS and 60.0 FPS

Review note

The React viewport remains a single generic host adapter in app.tsx; creating seven wrapper components would duplicate route/loading/evidence plumbing without making the library examples clearer. The existing host-facing optional entry view remains isolated behind the new factories; replacing it with seven exact runtime-state unions is intentionally outside this behavior-preserving structure change.