fix: Run dev command only for core packages (no-changelog) (#7928)

## Summary
Provide details about your pull request and what it adds, fixes, or
changes. Photos and videos are recommended.

- Filters out `@n8n/chat` and `n8n-design-system` from `pnpm run dev`
- Fixes dev/build error appearing due to code string `import ... from
'@n8n/chat'`

#### How to test the change:
1. `pnpm run dev` should work as expected
2. The command should not run for the two packages above
3. The error regarding `@n8n/chat` should no longer appear


## Issues fixed
Include links to Github issue or Community forum post or **Linear
ticket**:
> Important in order to close automatically and provide context to
reviewers


https://linear.app/n8n/issue/PAY-1089/run-dev-command-only-for-core-packages


## Review / Merge checklist
- [x] PR title and summary are descriptive. **Remember, the title
automatically goes into the changelog. Use `(no-changelog)` otherwise.**
([conventions](https://github.com/n8n-io/n8n/blob/master/.github/pull_request_title_conventions.md))
- [x] [Docs updated](https://github.com/n8n-io/n8n-docs) or follow-up
ticket created.
- [x] Tests included. N/A
> A bug is not considered fixed, unless a test is added to prevent it
from happening again. A feature is not complete without tests.
  >
> *(internal)* You can use Slack commands to trigger [e2e
tests](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#a39f9e5ba64a48b58a71d81c837e8227)
or [deploy test
instance](https://www.notion.so/n8n/How-to-use-Test-Instances-d65f49dfc51f441ea44367fb6f67eb0a?pvs=4#f6a177d32bde4b57ae2da0b8e454bfce)
or [deploy early access version on
Cloud](https://www.notion.so/n8n/Cloudbot-3dbe779836004972b7057bc989526998?pvs=4#fef2d36ab02247e1a0f65a74f6fb534e).

package.json

@@ -14,7 +14,7 @@
     "build:backend": "pnpm --filter=!@n8n/chat --filter=!n8n-design-system --filter=!n8n-editor-ui build",
     "build:frontend": "pnpm --filter=@n8n/chat --filter=n8n-design-system --filter=n8n-editor-ui build",
     "typecheck": "turbo run typecheck",
-    "dev": "turbo run dev --parallel",
+    "dev": "turbo run dev --parallel --filter=!n8n-design-system --filter=!@n8n/chat",
     "dev:ai": "turbo run dev --parallel --filter=@n8n/nodes-langchain --filter=n8n --filter=n8n-core",
     "clean": "turbo run clean --parallel",
     "format": "turbo run format && node scripts/format.mjs",