fix: Support satori/standalone on Cloudflare Workers

[levish0]

Fixes #878

satori/standalone has been broken on Cloudflare Workers since HarfBuzz landed in 0.33. Workers don't define self.location and won't compile wasm from bytes at runtime. HarfBuzz ran into that in three places:

1. the Emscripten glue reads self.location.href as soon as harfbuzzjs is imported
2. the inlined hb.wasm gets compiled at runtime
3. hbjs registers its blob destroy callback with addFunction, which compiles a tiny wasm module on the fly

What this changes:

• HarfBuzz starts on the first render instead of on import (the default build still preloads it)
• init({ layout, harfbuzz }) takes a precompiled module and hands it to Emscripten through instantiateWasm. init(layout) works like before.
• satori/harfbuzz.wasm is exported. It's copied from harfbuzzjs/hb.wasm at build time, so it's the same binary as the inlined one.
• harfbuzzjs patch: self.location?.href, and blobs use HB_MEMORY_MODE_DUPLICATE so they don't need a destroy callback
• test/workers-build.mjs imports the standalone build with Workers-like globals and renders once. It fails if any of the three fixes is reverted.

On Workers:

import satori, { init } from 'satori/standalone'
import layout from 'satori/layout.wasm'
import harfbuzz from 'satori/harfbuzz.wasm'

await init({ layout, harfbuzz })

Tested with the repro from #878 under wrangler dev. On main it fails with reading 'href'. On this branch it renders, with or without nodejs_compat and whether or not init is awaited. pnpm test passes, except the canvas tests, which I couldn't run locally (no native gl build).

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