Merged PR 2242: Refactor: New Appeal flow structural cleanup (Slices 1–8, no behaviour change)

## Summary

This PR merges the completed new-appeal refactor stream (Slices 1–8) into SIPS-Development.

This refactor was executed in controlled slices with regression validation at each step.

## Scope

Structural and readability improvements only:
- XML/form derivation extraction
- payload and file helper extraction
- side-effect facade introduction
- BuildSection and BuildCheckSection decomposition
- BuildCheckRow formatter map refactor
- nested prop boundary cleanup
- start-flow cleanup (CreateCase / AboutYou)

## Behaviour

No intended behavioural changes.

The following were explicitly preserved:
- S78 journey behaviour
- payload shapes and field names/ids
- HASCAS mapping logic
- appellant/agent branching
- validation rules and messages
- redirect/query parameters (`lpa`, `apt`, `id`)
- navigation and side-effect sequencing
- EN/CY output parity

## Validation

Full regression has been performed on:
- start flow (CreateCase / AboutYou)
- save and resume flows
- file upload handling
- check answers rendering
- submit/finalisation sequence
- confirmation flow
- CRM insertion path
- EN/CY parity

Additional checks:
- docsOffline branch behaviour
- completion and partial-save email paths
- negative-path validation scenarios
- lint (warnings baseline unchanged)

## Risk

Low:
- changes are structural only
- no business logic changes
- no contract changes

## Rollback

Safe rollback via reverting this merge commit.

## Notes

This refactor reduces coupling and prepares the new-appeal flow for future appeal-type expansion.

Related work items: #22570, #22576, #22577, #22583, #22586, #22587, #22588, #22590

components/newappeal/buildSection/ErrorSummary.js

@@ -0,0 +1,31 @@
+const ErrorSummary = ({ hasErrors, errorItems }) => {
+    return hasErrors ? (
+        <div
+            className="govuk-error-summary"
+            aria-labelledby="error-summary-title"
+            role="alert"
+            tabIndex="-1"
+            data-module="govuk-error-summary"
+        >
+            <h2 className="govuk-error-summary__title" id="error-summary-title">
+                The following fields have a problem :
+            </h2>
+            <div className="govuk-error-summary__body">
+                <ul className="govuk-list govuk-error-summary__list">
+                    {errorItems.map((item, i) => (
+                        <li key={i}>
+                            <a href={"#" + item.field + "_label"}>
+                                {" "}
+                                {item.label}
+                            </a>
+                        </li>
+                    ))}
+                </ul>
+            </div>
+        </div>
+    ) : (
+        ""
+    );
+};
+
+export default ErrorSummary;

components/newappeal/buildSection/PrimaryActionButtons.js

@@ -0,0 +1,5 @@
+const PrimaryActionButtons = ({ children }) => {
+    return <div className="govuk-button-group">{children}</div>;
+};
+
+export default PrimaryActionButtons;

components/newappeal/buildSection/SaveStatusIndicator.js

@@ -0,0 +1,14 @@
+const SaveStatusIndicator = ({ text }) => {
+    return (
+        <span className=" progress-save-active">
+            {text}
+            <img
+                className="data-loading-icon"
+                src="/assets/images/loading.gif"
+                alt={text}
+            />
+        </span>
+    );
+};
+
+export default SaveStatusIndicator;

components/newappeal/buildSection/SectionHeader.js

@@ -0,0 +1,5 @@
+const SectionHeader = ({ title }) => {
+    return <h1 className="govuk-heading-m  ">{title}</h1>;
+};
+
+export default SectionHeader;

components/newappeal/buildSection/SidebarProgressPanel.js

@@ -0,0 +1,12 @@
+const SidebarProgressPanel = ({ children }) => {
+    return (
+        <div className="govuk-grid-column-one-third">
+            <div className="at-nav-container">
+                {children}
+                <hr className="govuk-section-break govuk-section-break--m govuk-section-break--visible" />
+            </div>
+        </div>
+    );
+};
+
+export default SidebarProgressPanel;