rproxy and servewaf replace the one-process smallwebwaf (closes #172, closes #165)

`smallwebwaf` with no command now prints the commands and exits with status 2.
The image runs rproxy, or servewaf with SMALLWEBWAF_COMMAND=servewaf. The
passing-on code, its settings and its log fields and metric go. internal/proxy
keeps the checks, answers, reports and own endpoints; its tests run through the
real rproxy. The documents describe the pair.

Judgement call: clients.json keeps token_refused, since state files refuse unknown fields.
Deviation: script/gitea-requests sets SWWAF_LOG_REQUEST_HEADERS, to label requests.

Model: opus-5-5

docs/gitea.md

@@ -2,10 +2,11 @@
 
 These notes record what `smallwebwaf` does in front of gitea at the default
 settings. They are observations, not requirements; the requirements are in
-[`SPEC.md`](../SPEC.md). `script/gitea-requests` runs gitea behind the image and
-sends through it a sample of gitea's ordinary use and the requests named below.
-It reports each request the Core Rule Set refuses, so that these notes can be
-checked again when gitea or the Core Rule Set changes version.
+[`SPEC.md`](../SPEC.md). `script/gitea-requests` runs gitea behind `rproxy` and
+`servewaf`, and sends through them a sample of gitea's ordinary use and the
+requests named below. It reports each request the Core Rule Set refuses, so that
+these notes can be checked again when gitea or the Core Rule Set changes
+version.
 
 ## What the defaults cover
 
@@ -13,7 +14,7 @@ checked again when gitea or the Core Rule Set changes version.
   by it.
 - A clone is a response. It fits the defaults of 30 minutes and 1 GiB unless the
   repository is large or the link slow. A repository whose clone is larger than
-  1 GiB needs `SWWAF_RESPONSE_MAX_BYTES` raised, and the byte limits with it
+  1 GiB needs `SWRP_MAX_RESPONSE_SIZE` raised, and the byte limits with it
   ("Byte limits, per client" in `SPEC.md`).
 - A push is a request, and so is every other upload:
     - a git push;
@@ -23,10 +24,9 @@ checked again when gitea or the Core Rule Set changes version.
     - a release attachment.
 
     At the defaults, an upload larger than 100 MiB or taking more than 60
-    seconds is cut off ("Size and time limits" in `SPEC.md`). A gitea that takes
-    large uploads needs `SWWAF_REQUEST_MAX_BYTES`,
-    `SWWAF_CLIENT_REQUEST_TIMEOUT` and `SWWAF_UPSTREAM_REQUEST_TIMEOUT` raised
-    to fit.
+    seconds is cut off ("`rproxy`'s limits" in `SPEC.md`). A gitea that takes
+    large uploads needs `SWRP_MAX_REQUEST_SIZE` and `SWRP_MAX_REQUEST_TIME_MS`
+    raised to fit.
 
 - Archive download and blame or history pages are what scrapers hammer. The
   request limits do most of the work there.