fix(cli): compress the embedded web UI at brotli's best quality

[Hona]

The embedded web UI compresses once per release, so it now uses brotli's best quality, 11, instead of 6. Each asset compresses on the thread pool, in parallel.

Windows x64, OPENCODE_CHANNEL=prod	Before (#53643)	This PR	Change
CLI (opencode.exe)	206.8 MB	203.8 MB	−3.0 MB
Desktop installer (NSIS)	244.3 MB	241.4 MB	−2.9 MB
Node CLI (opencode2-node.exe)	177.7 MB	174.7 MB	−3.0 MB
Embedded web UI	27.0 MB	24.0 MB	−11%

Web UI by type	Quality 6	Quality 11
JS, CSS, HTML	7.1 MB	6.5 MB
Fonts	9.0 MB	8.3 MB
WASM	10.4 MB	8.7 MB

• Cost: about 30 to 60 seconds more per release build. The archive builds once per build, not once per target.
• A larger window (lgwin 24) saved only another 0.1 MB, so this keeps the default.

function compress(body: Buffer) {
  return promisify(brotliCompress)(body, {
    params: { [constants.BROTLI_PARAM_QUALITY]: 11, [constants.BROTLI_PARAM_SIZE_HINT]: body.length },
  })
}

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