artifacts: archive non-report dirs at their own paths, list them on the artifact page

Every artifactDir landed below reports/ — the legacy
archived_artefact_dir_path layout — which mislabeled non-report outputs
(reports/werkdock/dist/werkdock) AND hid them: the artifact page's
report index only scans reports/ for HTML pages, so a built binary was
stored but never shown.

Now build/reports keeps archiving as reports/ (the browsable anchor and
every existing link), every other directory archives at its
workspace-relative path, and the artifact page gains a plain-files list
for everything outside reports/ (log files stay in their own section;
capped at 200 entries). Existing stored artifacts keep their old layout
and remain served; only new builds use the new one.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main/resources/templates/artifact.html

@@ -70,7 +70,13 @@
                       th:text="${report.failures} + ' failed'">2 failed</span>
             </li>
         </ul>
-        <p th:if="${#lists.isEmpty(reportIndexes)}" class="muted">
+        <ul th:if="${!#lists.isEmpty(fileArtifacts)}">
+            <li th:each="file : ${fileArtifacts}">
+                <a th:href="${filesBase} + '/' + ${file}" target="_blank"
+                   rel="noopener noreferrer" th:text="${file}">werkdock/dist/werkdock</a>
+            </li>
+        </ul>
+        <p th:if="${#lists.isEmpty(reportIndexes) and #lists.isEmpty(fileArtifacts)}" class="muted">
             No artifact directories were produced by this build.
         </p>
     </article>