Fix HttpServerResponse.fromWeb losing Content-Type header

[kitlangton]

Summary

• Fix HttpServerResponse.fromWeb to preserve the Content-Type header when converting a web Response to HttpServerResponse
• Previously, when the response had a body, the Content-Type was not passed to Body.stream(), causing it to default to application/octet-stream
• This affected any code using HttpApp.fromWebHandler to wrap web handlers (e.g., integrating third-party auth libraries like Better Auth)

Test Plan

• Added test preserves response content-type header - verifies JSON responses have correct content-type
• Added test preserves custom content-type header - verifies custom content-types like text/html are preserved
• Added test json preserves content-type - verifies toWebHandler correctly outputs content-type

All 175 tests pass.

Example

Before this fix, wrapping a web handler would lose the Content-Type:

const webHandler = async () => Response.json({ message: "hello" })
const app = HttpApp.fromWebHandler(webHandler)
const handler = HttpApp.toWebHandler(app)
const response = await handler(new Request("http://localhost/"))

// Before: response.headers.get("Content-Type") === "application/octet-stream" ❌
// After:  response.headers.get("Content-Type") === "application/json" ✅

[changeset-bot]

🦋 Changeset detected

Latest commit: 1e1cac7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 31 packages

Name	Type
@effect/platform	Patch
@effect/cli	Patch
@effect/cluster	Patch
@effect/experimental	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/rpc	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-drizzle	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-node	Patch
@effect/sql	Patch
@effect/workflow	Patch
@effect/ai	Patch
@effect/ai-amazon-bedrock	Patch
@effect/ai-anthropic	Patch
@effect/ai-google	Patch
@effect/ai-openai	Patch
@effect/ai-openrouter	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/sql-kysely	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[kitlangton]

Here's an example of the problem in context.

https://github.com/kitlangton/effect-better-auth-example/blob/main/src/server/middleware/BetterAuthApp.ts#L15