README and SPEC say what docker stop does to requests in progress when the app exits at once (closes #139)

runit stops smallwebwaf and the app at the same time, so the five seconds
smallwebwaf gives requests in progress help only while the app still
answers them. Both documents now say so, say what the client gets when the
app exits at once on SIGTERM, and say what an app does to let its requests
in progress finish.

Model: opus-5-5

README.md

@@ -1958,9 +1958,10 @@ main "$@"
   `smallwebwaf` then stops taking requests and gives those in progress five
   seconds to finish, which they can do only while the app still answers. An app
   that exits at once on SIGTERM ends them: the client gets `502`, or a response
-  cut short if the app had already begun to answer. An app that should finish
-  its requests in progress keeps answering them for up to five seconds after
-  SIGTERM.
+  cut short if the app had already begun to answer. An app that should let them
+  finish keeps taking and answering requests, not only the ones it already has,
+  for the whole five seconds after SIGTERM, since `smallwebwaf` can still pass
+  it requests it took before then.
 
 A rule file is one rule per line: a name, what to match against, what to do, and
 a regex.

SPEC.md

@@ -1330,8 +1330,10 @@ The two processes:
   writes its state files as it stops (see "Persistent state"). The requests in
   progress can finish only while the app still answers. An app that exits at
   once on SIGTERM ends them: the client gets `502`, or a response cut short if
-  the app had already begun to answer. An app that should finish its requests in
-  progress keeps answering them for up to five seconds after SIGTERM.
+  the app had already begun to answer. An app that should let them finish keeps
+  taking and answering requests, not only the ones it already has, for the whole
+  five seconds after SIGTERM, since `smallwebwaf` can still pass it requests it
+  took before then.
 - The container's root filesystem stays writable: runit writes each service's
   status into its directory under `/etc/service`.