Name log fields, metrics and the Core Rule Set package for what they are (closes #192)

The first half of the naming audit: names now say what they are. `internal/waf` is `internal/coreruleset`. Log fields, the action `blocked_by_core_rule_set`, the metric and the alert event say Core Rule Set. Timings end `_ms`. Percentages say of what, as `rate_limit_percent` and `bytes_limit_percent`. Setting names follow in #234.

Judgement call: `blocked_by_core_rule_set`, not the audit's `core_rule_set_blocked`, to match `blocked_by_block_rule`.
Trips a reader: an existing state file holding `waf_blocked` or the anomaly scope `watch` stops the start and must be removed. `SWW_ALERT_EVENTS` listing `waf_block` must list `core_rule_set_match`.

Model: opus-5-5

internal/sww/sww.go

@@ -22,6 +22,7 @@ import (
 
 	"sneak.berlin/go/smallwebwaf/internal/alerts"
 	"sneak.berlin/go/smallwebwaf/internal/config"
+	"sneak.berlin/go/smallwebwaf/internal/coreruleset"
 	"sneak.berlin/go/smallwebwaf/internal/discriminator"
 	"sneak.berlin/go/smallwebwaf/internal/lookup"
 	"sneak.berlin/go/smallwebwaf/internal/remotelog"
@@ -29,7 +30,6 @@ import (
 	"sneak.berlin/go/smallwebwaf/internal/requestlog"
 	"sneak.berlin/go/smallwebwaf/internal/rules"
 	"sneak.berlin/go/smallwebwaf/internal/state"
-	"sneak.berlin/go/smallwebwaf/internal/waf"
 )
 
 // shutdownTimeout is how long requests in progress may take to finish
@@ -197,7 +197,7 @@ func RunDiscriminator(ctx context.Context, params Params) int {
 func newServer(
 	cfg *config.Config, stdout io.Writer, processLog *slog.Logger,
 	now func() time.Time, ruleFiles *rules.Files, alertQueue *alerts.Queue,
-	crs *waf.CoreRuleSet,
+	crs *coreruleset.CoreRuleSet,
 ) (*discriminator.Server, error) {
 	var lookupFile *lookup.File