docs(protocol): drop the phantom configSchema manifest file-map row from plugin-spec (#13697)

The `objectstack.config.ts` example on content/docs/protocol/kernel/plugin-spec.mdx
carried a `configSchema: 'src/config.schema.ts'` row at the tail of its `metadata:`
file-map. `packages/spec/src/kernel/manifest.zod.ts` declares no such key -- and
because `ManifestSchema` is not `.strict()`, an author who copies the example gets
no error at all: the key is silently stripped and the file is never loaded.

Only the manifest file-map row is removed. The page's "Configuration Schema"
section and best-practice 4 (`configSchema.parse(this.options)` in `init`) describe
the plugin-owned self-parse pattern, which is real and is untouched -- the same
identifier means two different things on this page.


Claude-Session: https://claude.ai/code/session_01Pk26oZ12t5N1hwGW1m1MgC

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-project-manager

content/docs/protocol/kernel/plugin-spec.mdx

@@ -96,9 +96,6 @@ export default definePlugin({
     translations: [
       'i18n/**/*.json',
     ],
-    
-    // Configuration schema
-    configSchema: 'src/config.schema.ts',
   },
 
   // NOTE: there is no `lifecycle` file-map. Earlier revisions of this page