README states what refused reports, one sender and nginx's 413 do (closes #145, closes #146, closes #147)

The README said the page keeps refused samples and sends them later.
Those in the 100-round history are sent only while it holds them: at
the 1-second interval one refused report loses the oldest 20 seconds of
each host's samples, and a pause longer than the history loses every
sample between the last delivered report and the pause. Samples an
interval change cleared are kept apart, the last 100 per host, until
delivered. Report limits now says one address at the defaults can fill
the 1 GiB cap in about 17 minutes. In the image, nginx answers a body
over 1 MiB itself, with 413 and an HTML page; the backend's own 413
sentences now apply to it run on its own.

Model: opus-5-5

TODO.md

@@ -21,6 +21,23 @@ Run `make frontend-viewport-test` in CI as its own step; it is not part of
 
 # Completed Steps
 
+- 2026-10-18: `README.md` says what the page loses while reports are refused or
+  the page is paused ([#145](https://git.eeqj.de/sneak/netwatch/issues/145)),
+  how fast one address can replace the stored reports
+  ([#146](https://git.eeqj.de/sneak/netwatch/issues/146)), and that in the image
+  nginx answers a body over 1 MiB itself
+  ([#147](https://git.eeqj.de/sneak/netwatch/issues/147)). A sample in the
+  history that no report has delivered is sent only as long as the history holds
+  it: at the 1-second interval one refused or failed report loses the oldest 20
+  seconds of each host's samples, and a pause longer than the history loses
+  every sample between the last delivered report and the pause. Samples an
+  interval change cleared are kept apart, the last 100 per host, until they are
+  delivered. At the defaults, one address sending 1 MiB reports made up to
+  compress badly can fill the 1 GiB cap in about 17 minutes. nginx's
+  `client_max_body_size` is also 1 MiB by default, so in the image it answers a
+  larger body with 413 and its own HTML page, and the backend never sees or
+  records it; the backend's own 413 sentences now say they apply to it run on
+  its own. The reporter, the body limit and nginx are unchanged
 - 2026-10-18: a browser that cannot format the header's clocks still probes
   ([#149](https://git.eeqj.de/sneak/netwatch/issues/149)). The clocks name the
   local time zone through `Intl.DateTimeFormat`'s `shortGeneric` option, which