Move twenty-client-sdk to dev dep (#21611)

# Introduction
The `twenty-client-sdk` is always provided and injected at runtime by
the twenty-server instance
Which mean that even if in your app locally you're using
twenty-client-sdk `1.0` installing this app on twenty instance `2.0`
will result in injecting another `twenty-client-sdk`

That's the expected behavior and tradeof

The twenty-app devdep should only be used to guide local devxp following
typesafety and so on

A user can still locally generated its own twenty-client-sdk and publish
it if necessary

<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/21611?utm_source=github"
target="_blank" rel="noopener noreferrer"
data-no-image-dialog="true"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"><source
media="(prefers-color-scheme: light)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-light.svg"><img
alt="Review in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"></picture></a>
<!-- End of auto-generated description by cubic. -->

packages/twenty-docs/developers/extend/apps/getting-started/project-structure.mdx

@@ -38,3 +38,24 @@ my-twenty-app/
 <Note>
 **File organization is up to you.** The folders above are conventions — the SDK detects entities via AST analysis on `export default defineEntity(...)` calls regardless of where the file lives.
 </Note>
+
+## Dependencies
+
+Both Twenty SDK packages belong under `devDependencies`, not `dependencies`:
+
+```json filename="package.json"
+{
+  "dependencies": {},
+  "devDependencies": {
+    "twenty-client-sdk": "^2.13.0",
+    "twenty-sdk": "^2.13.0"
+  }
+}
+```
+
+- **`twenty-sdk`** ships the `twenty` CLI and the build/scaffolding tooling. It only runs at development and build time and is never imported by your published app's runtime.
+- **`twenty-client-sdk`** _is_ imported by your app code (`CoreApiClient`, `MetadataApiClient`, `RestApiClient`), but Twenty provides it at runtime — logic functions get it from a generated SDK layer, and front components resolve it from server-served modules. Your installed copy is only used for typechecking and the deploy-time build, so it never needs to ship in the deployed bundle.
+
+Keeping either package under `dependencies` pulls it into the installed app's runtime bundle, where it is dead weight. `twenty build` emits a warning when either is still listed under `dependencies`.
+
+Add your app's own runtime dependencies (libraries your logic functions actually import at runtime) under `dependencies` as usual.

packages/twenty-docs/developers/extend/apps/getting-started/troubleshooting.mdx

@@ -9,5 +9,6 @@ icon: "wrench"
 - **Yarn 4 missing** — Run `corepack enable`.
 - **Dependencies broken** — `rm -rf node_modules && yarn install`.
 - **`twenty-sdk` errors after upgrading to v2.8.0** — It moved from `dependencies` to `devDependencies` in v2.8.0. See [Project Structure → Dependencies](/developers/extend/apps/getting-started/project-structure#dependencies).
+- **`twenty build` warns about `twenty-client-sdk` under `dependencies`** — It is provided at runtime by Twenty, so it should be moved to `devDependencies` alongside `twenty-sdk`. See [Project Structure → Dependencies](/developers/extend/apps/getting-started/project-structure#dependencies).
 
 Stuck? Ask on the [Twenty Discord](https://discord.com/channels/1130383047699738754/1130386664812982322).