docs(frontend): add mandatory pre-completion checks to CLAUDE.md (#12161)

### Changes 🏗️

Adds a **Pre-completion Checks (MANDATORY)** section to
`frontend/CLAUDE.md` that instructs Claude Code agents to always run the
following commands in order before reporting frontend work as done:

1. `pnpm format` — auto-fix formatting issues
2. `pnpm lint` — check for lint errors and fix them
3. `pnpm types` — check for type errors and fix them

This ensures code quality gates are enforced consistently by AI agents
working on the frontend.

### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
  - [x] Verified `pnpm format` passes cleanly
  - [x] Verified `pnpm lint` passes cleanly
  - [x] Verified `pnpm types` passes cleanly

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: 0ubbe

autogpt_platform/frontend/CLAUDE.md

@@ -30,6 +30,16 @@ pnpm format
 pnpm types
 ```
 
+### Pre-completion Checks (MANDATORY)
+
+After making **any** code changes in the frontend, you MUST run the following commands **in order** before reporting work as done, creating commits, or opening PRs:
+
+1. `pnpm format` — auto-fix formatting issues
+2. `pnpm lint` — check for lint errors; fix any that appear
+3. `pnpm types` — check for type errors; fix any that appear
+
+Do NOT skip these steps. If any command reports errors, fix them and re-run until clean. Only then may you consider the task complete. If typing keeps failing, stop and ask the user.
+
 ### Code Style
 
 - Fully capitalize acronyms in symbols, e.g. `graphID`, `useBackendAPI`
@@ -74,3 +84,4 @@ See @CONTRIBUTING.md for complete patterns. Quick reference:
    - Do not use `useCallback` or `useMemo` unless asked to optimise a given function
    - Do not type hook returns, let Typescript infer as much as possible
    - Never type with `any` unless a variable/attribute can ACTUALLY be of any type
+   - avoid index and barrel files