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.

packages/examples/jsonrpc-demo/src/index.ts

@@ -0,0 +1,9 @@
+/**
+ * Bin-only app package: `bin.ts` discovers an external `cordis.yml` and owns
+ * process exit. This module exports no composition plugin; the config chooses
+ * whether to load the {@link @deepseek-ai/dsh-jsonrpc} serving plugin.
+ *
+ * @module @deepseek-ai/dsh-jsonrpc-demo
+ */
+
+export {}