fix(server): serve html assets with utf-8 charset

[talkingdonkeyz]

What Changed

The /api/assets route served workspace HTML files with a bare text/html content type. It now sends text/html; charset=utf-8 for .html/.htm files, plus tests for the header.

Why

Opening an HTML file in the built-in browser garbles any non-ASCII text unless the file declares its own <meta charset> (agents often don't). The asset response has no charset and sets X-Content-Type-Options: nosniff, so Chromium falls back to windows-1252 and UTF-8 content renders as mojibake (你好 becomes ä½ å¥½).

HTML is the only type that needs this: CSS and module scripts already default to UTF-8, classic scripts inherit the document's encoding, and SVG is XML which is UTF-8 by default.

UI Changes

Same file served without and with the fix:

Before:

After:

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes (N/A)

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Note

Low Risk
Narrow header change on the asset route with tests; no auth, data, or routing logic changes.

Overview
Workspace HTML files served from /api/assets now get Content-Type: text/html; charset=utf-8 for .html and .htm paths (case-insensitive), instead of a bare text/html from the file response.

That aligns asset responses with the built-in browser expectation so UTF-8 text renders correctly when pages lack their own <meta charset>, especially with X-Content-Type-Options: nosniff already set on these responses.

Tests cover .html/.htm and uppercase .HTM; SVG sandbox headers and other asset types are unchanged.

^{Reviewed by Cursor Bugbot for commit 9e42ae6. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Serve HTML assets with Content-Type: text/html; charset=utf-8 in assetResponseHeaders

Updates assetResponseHeaders to set Content-Type: text/html; charset=utf-8 for .html and .htm files (case-insensitive). Previously, HTML assets were served without an explicit charset, which could cause encoding issues in browsers.

^{Macroscope summarized 9e42ae6.}

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[macroscopeapp]

Approvability

Verdict: Approved 9e42ae6

Simple bug fix adding UTF-8 charset header for HTML assets. The change follows the existing pattern for SVG files in the same function and includes test coverage.

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