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.
Partially verified: make example-app and make gitea-requests never built the image, as Ubuntu's snapshot service answered 5xx.

Model: opus-5-5

internal/proxy/lookup_test.go

@@ -1,9 +1,7 @@
 package proxy_test
 
 import (
-	"net"
 	"net/http"
-	"net/http/httptest"
 	"net/netip"
 	"path/filepath"
 	"slices"
@@ -142,7 +140,7 @@ func TestRequestThatWaitedForItsLookupIsCountedWhenItGoesOn(t *testing.T) {
 		t.Fatalf("first request: %v", err)
 	}
 
-	wantLine(t, out.requestLines(t, 2)[1], http.StatusOK, requestlog.ActionForward)
+	wantLine(t, out.endedLines(t, 2)[1], http.StatusOK, requestlog.ActionForward)
 
 	// The third request's count holds all three: the first was counted
 	// when it went on, in the minute under way, and the second's count
@@ -150,7 +148,7 @@ func TestRequestThatWaitedForItsLookupIsCountedWhenItGoesOn(t *testing.T) {
 	clk.advance(500 * time.Millisecond)
 	wantStatus(t, do(t, requestFromDE()), http.StatusOK)
 
-	if got := out.requestLines(t, 3)[2].Counts.Minute; got != 3 {
+	if got := out.endedLines(t, 3)[2].Counts.Minute; got != 3 {
 		t.Errorf("the third request's count in the minute is %v, want 3", got)
 	}
 }
@@ -387,18 +385,15 @@ func TestRequestWaitsAsLongAsTheLookupTimeoutSays(t *testing.T) {
 		// is never reached.
 		const timeout = 3 * time.Second
 
-		server, out, _ := newProxy(t, "http://app.invalid", unansweredGeoJSURL,
-			time.Now, map[string]string{
+		server, out, _ := newServeWAF(t, unansweredGeoJSURL, time.Now,
+			map[string]string{
 				lookupTimeout:    timeout.String(),
 				allowedCountries: "DE",
 			})
 
-		req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/",
-			http.NoBody)
-		req.RemoteAddr = net.JoinHostPort(fromDE, "1234")
 		began := time.Now()
 
-		server.Handler.ServeHTTP(httptest.NewRecorder(), req)
+		serveFromDE(t, server, http.MethodGet, http.NoBody)
 
 		if waited := time.Since(began); waited != timeout {
 			t.Errorf("the request waited %s for its answer, want %s", waited, timeout)