fix: register the examples/ group in the tsconfig paths map

The @deepseek-ai/dsh-* wildcard maps each package name to its group's
src; the new packages/examples/ group needs its own glob, or the four
moved packages fall back to unbuilt lib/ and vitest cannot resolve them.
Also update the moved specs' plugin export-name assertions (acp-agent ->
acp-demo, stdio-agent -> stdio-demo, agent-core -> agent-spine-demo).

tsconfig.base.json

@@ -60,6 +60,7 @@
         "./packages/session-persistence/*/src",
         "./packages/session-query/*/src",
         "./packages/ui/*/src",
+        "./packages/examples/*/src",
         "./packages/util/*/src",
         "./packages/mcp/*/src",
         "./packages/support/*/src"