docs: add in-depth comparison vs Bun and Deno

[robertsLando]

Summary

• New guide page pkg vs Bun vs Deno (docs-site/guide/vs-bun-deno.md) covering native addons, bundle format, cross-compile, bytecode, and binary size across @yao-pkg/pkg (Standard + SEA), bun build --compile, and deno compile.
• Real case study bundling @anthropic-ai/claude-code@1.0.100 with all three tools — the last pre-native ESM release, which stresses ESM + top-level await, WASM assets, vendored binaries, and optional native deps. Includes measured binary sizes (108 MB → 194 MB) and best-of-5 cold-start times (797 ms → 1256 ms).
• Final-verdict section with a lane-by-lane recommendation.
• Explicit "Be critical" section that pushes back on claims readers might infer (e.g. "V8 > JSC", "bytecode = encrypted source", "pkg Standard ships stock Node.js" — it doesn't; only SEA does).
• Sidebar nav entry added between SEA vs Standard and Migration from vercel/pkg.

Test plan

• yarn lint:style passes on the new page and config change
• npm run docs:build inside docs-site/ completes cleanly (generates dist/guide/vs-bun-deno.html)
• Mermaid diagram renders (uses the existing flowchart pipeline)
• Spot-check the rendered page on the deployed docs site after merge

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