fix: judge evidence alt text with asset metadata, not syntax

The parser has no asset catalogue, so it cannot know whether an
evidence figure is decorative. Move the empty-alt rejection from
parse-time (a syntax error) to publish validation, where the mock
treats static evidence assets as decorative: false since the static
registry predates the Asset capability. The real rule is that the
server judges alt against Asset.decorative.

src/features/tech-log/adapters/mock/validate-working-copy.ts

@@ -165,6 +165,11 @@ export function validateWorkingCopy(document: WorkingCopy, dependencies: Validat
       for (const block of parseCaseContent(document.bodyMarkdown)) if (block.type === "EVIDENCE_FIGURE") {
         if (!isSupportedEvidenceKey(block.key)) error("EVIDENCE_UNSUPPORTED", "/bodyMarkdown", `지원하지 않는 Evidence: ${block.key}`);
         else if (!dependencies.catalog.some((entry) => entry.type === "EVIDENCE" && (entry.id === block.key || entry.label === block.key || entry.publicPath === `/media/${block.key}.svg`))) error("EVIDENCE_NOT_FOUND", "/bodyMarkdown", `Evidence 없음: ${block.key}`);
+        else if (block.alt.trim().length === 0) {
+          // 정적 evidence 자산은 장식용이 아니다. Asset 기반 경로에서는 서버가
+          // Asset.decorative로 같은 판정을 한다.
+          error("EVIDENCE_ALT_REQUIRED", "/bodyMarkdown", `Evidence에 대체 텍스트가 필요합니다: ${block.key}`);
+        }
       }
     } catch { error("CONTENT_FORMAT_INVALID", "/bodyMarkdown", "지원하는 문법을 사용하세요."); }
     if (!document.lastVerifiedOn) error("LAST_VERIFIED_ON_REQUIRED", "/lastVerifiedOn", "검증일을 입력하세요."); else if (dependencies.now.getTime() - Date.parse(`${document.lastVerifiedOn}T00:00:00Z`) > 30 * 86_400_000) warning("VERIFICATION_OLDER_THAN_30_DAYS", "/lastVerifiedOn", "30일이 지났습니다.");

src/features/tech-log/domain/content-format/parse-case-content.ts

@@ -514,7 +514,9 @@ function directiveBlock(
       if (!/^[a-z0-9]+(?:-[a-z0-9]+)*$/u.test(attributes.key)) {
         invalid(node, `unsafe evidence key: ${attributes.key}`);
       }
-      if (!attributes.alt) invalid(node, "evidence alt text is required");
+      // alt 필요 여부는 Asset의 `decorative`에 달려 있어 여기서는 판단할 수
+      // 없다. 빈 alt는 구문 오류가 아니며 publish 검증이 Asset metadata와 함께
+      // 판정한다(설계 §7.7).
       if (attributes.zoom !== "true" && attributes.zoom !== "false") {
         invalid(node, "evidence zoom must be true or false");
       }