chore: import upstream snapshot with attribution

examples/stories/caching/README.md

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+# caching
+
+A server stamps `CacheableResult` hints (`ttl_ms`, `cache_scope`) onto list and
+read responses; a client honours them to skip redundant round-trips. The story
+will show per-result overrides on `@mcp.resource()` / `@mcp.tool()` and the
+client-side cache hit/miss path.
+
+**Status: not yet implemented.** Server-side stamping landed (defaults
+`ttl_ms=0`, `cache_scope="private"`), but the per-result override hook and the
+client honouring path are not implemented yet. An example today could only show
+the defaults being emitted, not acted on.
+
+## Spec
+
+[Caching — basic utilities](https://modelcontextprotocol.io/specification/draft/basic/utilities/caching)
+
+## Working example elsewhere
+
+The TypeScript SDK ships a runnable `caching` story:
+[typescript-sdk/examples/caching](https://github.com/modelcontextprotocol/typescript-sdk/tree/main/examples/caching).