feat(hub): built-in PBank 题库 capability + role tools (v0.0.42)

Register pbank as an ADR-0027 external capability with org-scoped
username/password envelopes, readiness via /login, and in-process
cph_hub MCP tools (search/get/get_many) that materialize sources under
the run workspace. Extend the capability secret payload for docmind vs
pbank kinds, admin capabilities UI, role tool umbrella `pbank`, and the
pbank-problem-report skill. Credentials never reach the Agent process.

hub/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@paradigm/hub",
-  "version": "0.0.41",
+  "version": "0.0.42",
   "private": true,
   "type": "module",
   "engines": {