Export the artifact ID pattern for host-side reference extraction

Why: Hosts also extract artifact IDs from text outside the gate;
sharing one compiled pattern keeps the forms aligned.

Evidence: additive export; the gates suite still passes.

Impact: ArtifactIDPattern exported; gate internals use it too.

runtime/gates/gates.go

@@ -39,10 +39,11 @@ type ArtifactRef struct {
 }
 
 var (
-	artIDRe      = regexp.MustCompile(`art_[0-9a-f]{12}`)
-	fileClaimRe  = regexp.MustCompile(`(?s)(?:已生成|已保存|已导出|已写入).{0,120}?\.(?:docx|xlsx|pptx|pdf|png|jpe?g|csv|md|txt|json)\b`)
-	softClaimRe  = regexp.MustCompile(`(?s)(?:文件|文档|工件).{0,40}?已(?:正常)?(?:生成|登记|保存|导出|写入)`)
-	forgedCallRe = regexp.MustCompile(`\[(?:调用工具|工具结果|产出工件) `)
+	// ArtifactIDPattern 是工件编号的文本形态（门禁与宿主的引用提取共用）。
+	ArtifactIDPattern = regexp.MustCompile(`art_[0-9a-f]{12}`)
+	fileClaimRe       = regexp.MustCompile(`(?s)(?:已生成|已保存|已导出|已写入).{0,120}?\.(?:docx|xlsx|pptx|pdf|png|jpe?g|csv|md|txt|json)\b`)
+	softClaimRe       = regexp.MustCompile(`(?s)(?:文件|文档|工件).{0,40}?已(?:正常)?(?:生成|登记|保存|导出|写入)`)
+	forgedCallRe      = regexp.MustCompile(`\[(?:调用工具|工具结果|产出工件) `)
 )
 
 // ClaimGate 判断终轮正文是否在没有对应工件的情况下声称交付。
@@ -62,7 +63,7 @@ func ClaimGate(body string, produced []ArtifactRef, lookup ArtifactLookup) (bool
 		}
 	}
 	knownExisting := false
-	for _, id := range artIDRe.FindAllString(body, -1) {
+	for _, id := range ArtifactIDPattern.FindAllString(body, -1) {
 		if producedIDs[id] {
 			continue
 		}