• Adds informative error message to format check failure
• Guides users to run 'yarn format-fix' command
• Improves CI feedback clarity for formatting issues

Add error message to format check step

• Enhanced format check step with descriptive error message
• Added explicit exit code 1 on formatting mismatch
• Guides developers to run 'yarn format-fix' command
• Improves CI feedback for formatting failures

.github/workflows/CI.yml

Description

The added error message is placed after git diff --exit-code as a separate command, so when `git
diff --exit-code` exits non-zero (the normal case when formatting changes exist), the message is not
guaranteed to execute depending on shell error handling, undermining the PR goal of showing a
helpful message on formatting mismatch.

Code

.github/workflows/CI.yml[56]

+        run: yarn format || (yarn format-fix; git diff --exit-code; echo "Formatting did not match (see above diff), please run 'yarn format-fix'" >&2 && exit 1)

Evidence

The workflow runs git diff --exit-code before the echo ... message in a simple ;-sequenced
command list. When formatting mismatches exist, yarn format-fix will modify files and `git diff
--exit-code` will return non-zero; because the message is only executed after that command, it is
not robustly guaranteed to run in all CI shell configurations. The intent that format checks and
format-fix writes formatting is confirmed by the scripts in package.json.

.github/workflows/CI.yml[55-56]
package.json[20-21]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
The `Check format` step aims to print a helpful error message when formatting does not match. Currently the message is placed after `git diff --exit-code` in a `;`-sequenced list, which makes the message execution unreliable when `git diff` returns non-zero (the common “formatting changed” case) under some shell error-handling modes.

### Issue Context
- `yarn format` runs prettier in `--check` mode.
- On failure, the workflow runs `yarn format-fix` then `git diff --exit-code`.
- The message should be shown when formatting mismatches exist (i.e., when `git diff --exit-code` detects changes after `format-fix`).

### Fix Focus Areas
- .github/workflows/CI.yml[55-56]

### Suggested implementation approach
Replace the one-liner with a multi-line `run: |` script, e.g.:

```yaml
- name: Check format
 run: |
   if ! yarn format; then
     yarn format-fix
     if ! git diff --exit-code; then
       echo "Formatting did not match (see above diff), please run 'yarn format-fix'" >&2
     else
       echo "yarn format failed, but no formatting diff was produced; see logs above" >&2
     fi
     exit 1
   fi
```

This ensures the message prints deterministically and the step fails when `yarn format` fails.

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