perf(text): profile MTSDF baker phases

[thejustinwalsh]

Summary

• add a package-owned MTSDF baker profiler with small, medium, complete, and all coverage arguments
• instrument selection, outline extraction, texel generation, packing, KTX2 encoding, and GLB serialization in the shared optimized Rust pipeline
• measure the shipped Wasm host copy path and a real serial Node Worker, including linear-memory and isolated RSS high-water marks
• retain exact work counters, payloads, native and Wasm identities, and machine-labeled timing evidence
• scope compiled admission-module byte identity to its recorded host while requiring foreign hosts to reproduce portable contracts under reviewed ceilings

Finding

Texel generation accounts for 98.8% to 99.7% of measured native pipeline time. Complete Inter generates 7,233,197 texels, visits 227,327,416 colored edges, and spends 25,871.57 of 25,957.06 native milliseconds in texel generation. The shipped Wasm pass is 52,420.37 ms; copying its 39,175,608-byte response takes 4.51 ms and final Worker delivery takes 0.47 ms. This admits the adjacent-texel scalar/SIMD comparison and rejects packing, container, or transfer work as the next optimization target.

Evidence

• direct Wasm and real Worker artifacts are byte-identical for small, medium, and complete cases
• same-host evidence is exact; foreign-host evidence must retain the portable contract, synthetic output, zero imports, complete SHA-256 identity, and raw/optimized/gzip/Brotli budgets
• default and profiling Rust suites pass; profiling preserves exact bake results
• production Bitmap, MTSDF, and Slug host hashes and sizes remain unchanged
• this layer's fail-closed autoresearch provenance authenticates its canonical package-size record

Stack

Depends on #7. The adjacent-texel optimization experiment is layered above this measured boundary.