Targets whose home page redirects are checked at /robots.txt (closes #194)

The browser follows a redirect, so the figures for the AWS Console, Akamai,
B2 and the S3 regions also timed the page it led to, for B2 and S3 on
another host. The Google Cloud Console redirects only requests that do not
say they come from another site; browsers say so and get a 403 directly.
Each of these targets is now checked at /robots.txt on its own host, which
answers without a redirect. README.md says what a figure includes. Chrome
opens a new connection for most S3 checks, so far regions now read higher.

Model: opus-5-5

TODO.md

@@ -25,7 +25,7 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
 
 - 2026-10-26: a target whose home page answers with a redirect is checked at
   `/robots.txt` on the same host, which answers without one
-  ([#190](https://git.eeqj.de/sneak/netwatch/issues/190)). These are the AWS
+  ([#194](https://git.eeqj.de/sneak/netwatch/issues/194)). These are the AWS
   Console, Akamai, B2 and the 8 S3 regions, and the Google Cloud Console, whose
   home page redirects a request that does not say it comes from another site.
   The browser follows a redirect, so their figures also timed the page it led