Rename the program to sww and its deciding daemon to discriminator (closes #218)

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/rules/rules.go

@@ -1,5 +1,5 @@
 // Package rules reads the rule files: the plain text files in
-// SWWAF_RULES_DIR, one rule to a line, that each request is checked
+// SWW_RULES_DIR, one rule to a line, that each request is checked
 // against, as the "Rule files" section of SPEC.md describes. They are read
 // at start, and again once the directory has had no change for a short
 // time after one is edited, added or removed.
@@ -40,7 +40,7 @@ const (
 // extension ends the name of every rule file.
 const extension = ".rules"
 
-// quietTime is how long SWWAF_RULES_DIR must go without a change before
+// quietTime is how long SWW_RULES_DIR must go without a change before
 // the rule files are read again, so that a file still being written, such
 // as one saved in place, appended to or copied in with scp, is read only
 // once whole.
@@ -100,19 +100,19 @@ type Rule struct {
 
 // Params are what Load needs.
 type Params struct {
-	// Dir is the directory of the rule files (SWWAF_RULES_DIR).
+	// Dir is the directory of the rule files (SWW_RULES_DIR).
 	Dir string
-	// Enabled is SWWAF_RULES_ENABLED: while it is false, no file is read
+	// Enabled is SWW_RULES_ENABLED: while it is false, no file is read
 	// 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
@@ -271,7 +271,7 @@ func (f *Files) logRead(count int) {
 func read(dir string) ([]Rule, string, error) {
 	entries, err := os.ReadDir(dir)
 	if err != nil {
-		return nil, dir, fmt.Errorf("SWWAF_RULES_DIR cannot be read: %w", err)
+		return nil, dir, fmt.Errorf("SWW_RULES_DIR cannot be read: %w", err)
 	}
 
 	var rules []Rule
@@ -299,7 +299,7 @@ func read(dir string) ([]Rule, string, error) {
 // readFile appends the rules of the rule file at path to rules. places
 // are where each id read so far is, and gain those of the file.
 func readFile(path string, rules []Rule, places map[string]string) ([]Rule, error) {
-	data, err := os.ReadFile(path) //nolint:gosec // a rule file, in SWWAF_RULES_DIR
+	data, err := os.ReadFile(path) //nolint:gosec // a rule file, in SWW_RULES_DIR
 	if err != nil {
 		return nil, err
 	}