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 SWW_COMMAND setting, the OS user, and the state
and rules directories.

No logic changes. make check passes.

Model: deepseek-v4-pro

internal/rules/rules.go

@@ -106,13 +106,13 @@ type Params struct {
 	// and no rule loaded.
 	Enabled bool
 	// ProcessLog receives how many rules were read, and the error in a
-	// rule file edited while smallwebwaf runs.
+	// rule file edited while sww runs.
 	ProcessLog *slog.Logger
 	// Alerts receive a file_error alert for that error.
 	Alerts *alerts.Queue
 }
 
-// Files are the rule files of a running smallwebwaf, and the rules read
+// Files are the rule files of a running sww, and the rules read
 // from them. They are safe for concurrent use.
 type Files struct {
 	params Params