chore(mcp): changeset states the plugin version type is now string | undefined

Claude-Session: https://claude.ai/code/session_016GiHYRmLSNWTfbX9gVQkpz
Co-Authored-By: Claude <noreply@anthropic.com>

Author: claude

.changeset/21532-mcp-server-info-version-default.md

@@ -8,6 +8,5 @@ Clause-②: no
 
 - Before, `MCPServerPlugin` and `MCPServerRuntime` each defaulted to the literal `1.0.0`, so every deployment built without the option, `os serve`'s auto-registration included, answered `initialize` with `serverInfo.version` `1.0.0` whatever the installed `@objectstack/mcp` was. Both defaults now read the version from the package's own `package.json`, ESM and CJS alike.
 - An explicit `version` option (`MCPServerPluginOptions.version`, `MCPServerRuntimeConfig.version`) is still answered as given.
-- `new MCPServerPlugin().version`, the kernel plugin's own version, is the package version too, where it was `1.0.0`.
-- If the manifest cannot be read (a bundle with no `package.json` beside it), `serverInfo.version` says `unknown` and the plugin's own `version` is left unset, which both kernels accept, instead of a placeholder they would refuse.
+- `new MCPServerPlugin().version`, the kernel plugin's own version, is the package version too, where it was `1.0.0`. Its declared type is now `string | undefined`: if the manifest cannot be read (a bundle with no `package.json` beside it), `serverInfo.version` says `unknown` and the plugin's own `version` is left unset, which both kernels accept, instead of a placeholder they would refuse.
 - Pass `version` yourself to keep reporting a fixed string.