feat(text): prove external raster extension

[thejustinwalsh]

Summary

• add a private external glyph-debug raster package that owns its kind, descriptor, standalone companion GLB, static/runtime bakers, decoder, retained TSL adapter, bounded slack, dirty uploads, overflow, abort, and disposal
• publish the renderer-adapter batch types required by Text and preserve external resource resolvers through the shared RasterRuntime cache
• add a registered WebGPU/WebGL product proof that borrows one host renderer, restores finite renderer state, retains object and geometry identity, and produces visible deterministic frames
• record the extension findings, decision, package ownership, size evidence, and Milestone 10.4 closure in canonical OKF documentation

Public boundary evidence

The proof package imports only published @pmndrs/text entry points and its own pinned Three.js dependency. Tests cover deterministic embedded and external artifacts, authenticated resource resolution, warm retained updates, shrink, exact-capacity growth, fragmented dirty-range fallback, overflow replacement, failure preservation, abort, empty batches, and idempotent disposal. No core raster-kind switch or registration edit is required.

Verification

• complete Rust, TypeScript, package, integration, fuzz-smoke, and benchmark unit suites
• 19-case headless conformance suite and packed-consumer test
• focused hardware proof on WebGPU and forced WebGL2 with one borrowed renderer and identical visible output
• production benchmark build, package-size freshness/budgets, autoresearch freshness, formatting, lint, typechecks, and OKF validation

Browser core and each first-party runtime closure are 55 raw and 49 minified bytes smaller than the parent commit; validator, baker-host, and Wasm artifacts are unchanged.

Stack

Depends on #14.