refactor(code-runtime-python): move the package into packages/experimental

The CPython code runtime's complete public contract is experimental, so it
moves to packages/experimental per the experimental-packages rules: npm name
@deepseek-ai/dsh-experimental-code-runtime-python, private: true, no
publishConfig. All references updated (code-runtime READMEs, config-catalog
and module-graph regenerated with zh alignment, tsconfig paths, doc-standard
and workspace-constraints scripts, the fd-3 and settlement Agent Notes, and
the package README links); md-links and translation pairing pass, and the
suite still runs green.

packages/experimental/code-runtime-python/tsdown.config.ts

@@ -0,0 +1,16 @@
+import { defineConfig } from 'tsdown'
+
+/**
+ * Single ESM bundle. The Python-side code is not TypeScript and ships verbatim
+ * under `py/` (whitelisted in package.json `files`) — no build step needed.
+ */
+export default defineConfig({
+  entry: ['lib/types/index.js', 'lib/types/invariant.js'],
+  outDir: 'lib',
+  format: ['esm'],
+  platform: 'node',
+  target: 'es2024',
+  fixedExtension: false,
+  dts: false,
+  clean: false,
+})