Rename the program to sww and its deciding daemon to discriminator

The program is now sww, built from cmd/sww, with two modes: sww rproxy and
sww discriminator. servewaf becomes discriminator everywhere it names that
daemon: the package (internal/discriminator), its types, functions, files, the
discriminator_line log field, and its docs and tests.

smallwebwaf is left only where sneak's directive allows it: the documents'
product name, the git.eeqj.de/sneak/smallwebwaf URLs, and the Go module path
sneak.berlin/go/smallwebwaf. Everywhere else a name containing it takes the sww
form: the package (internal/sww), metric names (sww_*), the X-Sww-* headers,
the /_sww/ admin endpoints, the OS user, and the state and rules directories.
The SWWAF_ environment variables take the SWW_ form.

No logic changes. make check passes.

Model: deepseek-v4-pro

internal/rproxy/client.go

@@ -18,7 +18,7 @@ const (
 )
 
 // peerAddress is the address of the request's TCP peer, normally traefik, without
-// any IPv6 zone, which servewaf refuses.
+// any IPv6 zone, which discriminator refuses.
 func peerAddress(r *http.Request) netip.Addr {
 	addrPort, err := netip.ParseAddrPort(r.RemoteAddr)
 	if err != nil {
@@ -34,7 +34,7 @@ func peerAddress(r *http.Request) netip.Addr {
 // address outside them is the visitor; if every address in it is inside, the
 // leftmost is, and with no header, the peer. An entry that is not an address
 // ends the reading, since nothing to its left can be believed. The visitor's
-// address never has an IPv6 zone, which servewaf refuses.
+// address never has an IPv6 zone, which discriminator refuses.
 func clientAddress(
 	peer netip.Addr, forwardedFor []string, trusted []netip.Prefix,
 ) netip.Addr {