docs: add Fixture Data & Schemas section to Playwright test guidance (#10642)

## Summary

Add a "Fixture Data & Schemas" section to `docs/guidance/playwright.md`
so agents reference existing Zod schemas and TypeScript types when
creating test fixture data.

## Changes

- **What**: New section listing key schema/type locations (`apiSchema`,
`nodeDefSchema`, `jobTypes`, `workflowSchema`, etc.) to keep test
fixtures in sync with production types.

## Review Focus

Documentation-only change; no runtime impact.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10642-docs-add-Fixture-Data-Schemas-section-to-Playwright-test-guidance-3316d73d365081f5a234e4672b3dc4b9)
by [Unito](https://www.unito.io)

docs/guidance/playwright.md

@@ -112,6 +112,21 @@ Tags are respected by config:
 - Use realistic ComfyUI workflows for E2E tests
 - When multiple nodes share the same title (e.g. two "CLIP Text Encode" nodes), use `vueNodes.getNodeByTitle(name).nth(n)` to pick a specific one. Never interact with the bare locator when titles are non-unique — Playwright strict mode will fail.
 
+## Fixture Data & Schemas
+
+When creating test fixture data, import or reference existing Zod schemas and TypeScript
+types from `src/` instead of inventing ad-hoc shapes. This keeps test data in sync with
+production types.
+
+Key schema locations:
+
+- `src/schemas/apiSchema.ts` — API response types (`PromptResponse`, `SystemStats`, `User`, `UserDataFullInfo`, WebSocket messages)
+- `src/schemas/nodeDefSchema.ts` — Node definition schema (`ComfyNodeDef`, `InputSpec`, `ComboInputSpec`)
+- `src/schemas/nodeDef/nodeDefSchemaV2.ts` — V2 node definition schema
+- `src/platform/remote/comfyui/jobs/jobTypes.ts` — Jobs API Zod schemas (`zJobDetail`, `zJobsListResponse`, `zRawJobListItem`)
+- `src/platform/workflow/validation/schemas/workflowSchema.ts` — Workflow validation (`ComfyWorkflowJSON`, `ComfyApiWorkflow`)
+- `src/types/metadataTypes.ts` — Asset metadata types
+
 ## Running Tests
 
 ```bash