Add endpoint and button to download realm

[backspace]

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    1 files  ±0      1 suites  ±0   1h 43m 54s ⏱️ +14s
1 925 tests ±0  1 908 ✅ ±0  17 💤 ±0  0 ❌ ±0 
1 940 runs  ±0  1 923 ✅ ±0  17 💤 ±0  0 ❌ ±0 

Results for commit 099ce9f. ± Comparison against base commit 397e601.

♻️ This comment has been updated with latest results.

[backspace]

You can see the errors here. I tried for a while to come up with a better way, including splitting the template, moving the functions outside the class… this was the only way I found that worked.

[lukemelia]

@codex review this. in particular, I'm curious if the implementation in this PR requires the zip file for the full realm to be assembled in memory on the realm server. If so, could it be adjusted to stream instead?

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

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[lukemelia]

@codex Does the implementation in this PR mean that the entire zip file will be assembled in memory on the realm server? If so, could it be adjusted to stream as it adds/compresses instead?

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[lukemelia]

The answer to my question:

The server-side implementation already streams the zip — it does not assemble it in memory. Here's the key mechanism in packages/realm-server/handlers/handle-download-realm.ts:

• Line 149: An archiver stream is created: archiver('zip', { zlib: { level: 9 } })
• Line 161: ctxt.respond = false disables Koa's default response handling, giving manual control of the
  response stream
• Line 163: archive.pipe(ctxt.res) pipes the archive directly to the HTTP response — compressed chunks are
  written to the socket as they're produced
• Line 166: archive.directory(realmPath, false) reads files from disk incrementally and feeds them into
  the archive stream

So archiver reads files from the filesystem, compresses them, and writes chunks directly to the HTTP
response. The full zip is never materialized in a single buffer on the server.

However, the client side does buffer the entire response in memory. In
packages/host/app/components/operator-mode/code-submode/left-panel-toggle.gts:139:

let blob = await response.blob();

This collects the entire streamed response into a Blob in browser memory before triggering the download
via a temporary link. For very large realms this could be a concern in the browser, but it's a common
pattern and browser Blob handling is generally efficient. An alternative would be to use the
https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream piped to a
https://github.com/nickersgmh/streamsaver.js-style approach, or more simply, to just navigate the browser
directly to the download URL (via window.location or an tag with the href set to the endpoint) and let
the browser handle the download natively — which would avoid holding it all in JS memory. The auth token
would need to be handled differently in that case (e.g., via a short-lived query parameter or cookie
rather than an Authorization header).