feat(hub): concurrent multi-PDF convert_pdf_to_md + readable skills (v0.0.40)

Teachers convert many PDFs in one tool call with bounded Docmind concurrency.
Each item keeps its own output_dir/document.md and UsageFact; failures are
per-file. Mirror role skills to .cph/runtime-skills and CPH_RUNTIME_SKILLS_DIR
so agents can Read SKILL.md instead of dead .claude/sandbox stubs.

hub/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@paradigm/hub",
-  "version": "0.0.39",
+  "version": "0.0.40",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@paradigm/hub",
-      "version": "0.0.39",
+      "version": "0.0.40",
       "dependencies": {
         "@alicloud/credentials": "^2.4.5",
         "@alicloud/docmind-api20220711": "^1.4.15",