refactor: relocate demo app bundles to packages/examples/*-demo

Move the agent-spine bundle and the stdio/ACP/JSON-RPC app packages out of
core/ and ui/ into a new packages/examples/ group, renamed with a -demo
suffix so the npm name marks them as non-product surface:

  core/agent-core   -> examples/agent-spine-demo  (dsh-agent-spine-demo)
  ui/stdio-agent    -> examples/stdio-demo        (dsh-stdio-demo)
  ui/acp-agent      -> examples/acp-demo          (dsh-acp-demo)
  ui/jsonrpc-agent  -> examples/jsonrpc-demo      (dsh-jsonrpc-demo)

Update every code/config/test reference and reference-only doc mentions, and
regenerate module-graph, config-catalog, and doc-graphs. The jsonrpc bin
(dsh-jsonrpc-agent) and single-file exe (dsh-jsonrpc-agent-pkg) keep their
names; the SDK runtime-startup surface is reconciled separately.

examples/echo-agent/cordis.yml

@@ -3,7 +3,7 @@
 # No API key: the `mock-echo` adapter never touches the network.
 
 # Hot-module reload for the dev/demo loop (a leaf entry, not baked into
-# dsh-stdio-agent — it needs `node --expose-internals`, which `demo:echo` passes).
+# dsh-stdio-demo — it needs `node --expose-internals`, which `demo:echo` passes).
 - id: hmr
   name: '@cordisjs/plugin-hmr'
   config:
@@ -24,7 +24,7 @@
 
 # The app pre-creates `main` on the mock model and supplies logging, persistence, and readline UI.
 - id: stdio-agent
-  name: '@deepseek-ai/dsh-stdio-agent'
+  name: '@deepseek-ai/dsh-stdio-demo'
   config:
     model: mock-echo
     persona: 'You are echo-agent, a demo agent.'