The Core Rule Set, run by Coraza, on each request's method, URL and headers (closes #25)

Coraza v3.8.1 runs the Core Rule Set 4.25.0 (coraza-coreruleset v4.25.0)
after the rule files, with the six changes and the default
SWWAF_WAF_DISABLED_RULES that SPEC.md gives; no body, no response.
SWWAF_WAF_MODE, SWWAF_WAF_PARANOIA_LEVEL, SWWAF_WAF_ANOMALY_THRESHOLD and
SWWAF_WAF_EXEMPT_PATHS as specified; SWWAF_WAF_DISABLED_RULES refuses
900000 to 900999, smallwebwaf's own rules among them. A request with more
query parameters than Coraza reads, 1000, adds 5 (rule 900300). In block
mode a match is refused with 403, an offence counted toward the error
burst; in detect mode it is let through. Both log waf_rule_ids, waf_score
and duration_waf, raise waf_block, and count
smallwebwaf_waf_matches_total.

Judgement call: waf_block is raised in block mode too.
Deviation: no engine-error path; with no body read, Coraza cannot fail.

Model: opus-5-5

internal/proxy/reputation_test.go

@@ -725,6 +725,10 @@ func TestClientRefusedForAnOffenceIsCheckedWithAbuseIPDBAtItsNextRequest(t *test
 			"a block rule", blockedPath, http.StatusForbidden, requestlog.ActionRuleBlocked,
 			ratelimit.Offences{RuleBlocked: 1},
 		},
+		{
+			"the Core Rule Set", sqlInjection, http.StatusForbidden,
+			requestlog.ActionWAFBlocked, ratelimit.Offences{WAFBlocked: 1},
+		},
 		{
 			"a ban rule", probePath, http.StatusForbidden, requestlog.ActionBanned,
 			ratelimit.Offences{Attack: 1},
@@ -744,7 +748,7 @@ func TestClientRefusedForAnOffenceIsCheckedWithAbuseIPDBAtItsNextRequest(t *test
 			s, clk, server := startWithClock(t, "", map[string]string{
 				abuseIPDBKey: accountKey, reputationAction: actionLog,
 				rulesDir: writeRules(t, testRules), attackBanDuration: "1h",
-				trapPaths: trapPathList, metricsToken: token,
+				trapPaths: trapPathList, metricsToken: token, wafMode: block,
 			})
 
 			s.request(client, tc.path, tc.status, tc.action)