perf: parallelize TF2 cold map loading

[Hona]

Summary

• replay the threaded TF2 cold-load checkpoint onto merged PR Fix TF2 menu and projectile presentation #10 without dropping its GameUI, Particle material-state, viewmodel-depth, display-frame, or cache-recency changes
• run TF2 compilation through a cross-origin-isolated shared-memory Chromium WASM worker pool
• reuse prepared map, collision, visibility, model dependencies, and source-backed texture planes while removing repeated large hashes and copies
• add the BSP-prefetched cold-map profile; observed best Console-to-Ready time remains 6.527 seconds, with the 2-second roadmap target still in progress

Verification

• bun test: 310 passed
• bun run test:rust: passed all locked workspaces
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• bun run verify:tf2-wasm jump_beef
• production Vite build
• headed profile:cold-map reached Ready after conflict integration

Remaining

• world compilation, presentation compilation, and renderer upload remain serial barriers
• full verify:browser could not run because agent-browser is unavailable on PATH

Supersedes #11.

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