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

context/refactor-tracker.md

@@ -0,0 +1,110 @@
+# New Appeal Refactor Tracker
+
+Base branch for this tracker: `refactor`
+
+## Status
+
+Current slice: Slice 8 — Start Flow Cleanup (CreateCase / AboutYou)  
+Status: READY TO START
+
+---
+
+## Slice List
+
+### Slice 1 — XML/Form Derivation Extraction
+
+Status: COMPLETE
+
+- Extract XML parsing helpers into lib
+- Keep selectors identical
+- No behaviour change
+
+---
+
+### Slice 2a — Payload Cleanup Helpers
+
+Status: COMPLETE
+
+- Extract boolean normalization
+- Extract null/internal key stripping
+
+---
+
+### Slice 2b — File Merge/Dedupe Helpers
+
+Status: COMPLETE
+
+- Extract file list merge logic
+- Extract dedupe logic
+
+---
+
+### Slice 3 — Side Effect Facade
+
+Status: COMPLETE
+
+- Wrap existing service calls
+- No logic changes
+
+---
+
+### Slice 4 — BuildSection UI Extraction
+
+Status: COMPLETE
+
+---
+
+### Slice 5 — BuildCheckSection UI Extraction
+
+Status: COMPLETE
+
+---
+
+### Slice 6 — BuildCheckRow Formatter Map
+
+Status: COMPLETE
+
+---
+
+### Slice 7 — Props Boundary Cleanup
+
+Status: COMPLETE
+
+---
+
+### Slice 8 — Start Flow Cleanup (CreateCase / AboutYou)
+
+Status: COMPLETE
+
+---
+
+## Rules
+
+- Only work on ONE slice at a time
+- Do not move to next slice until current is COMPLETE
+- Do not combine slices
+- Preserve behaviour at all times
+
+## Notes
+
+- Save/resume payload shape is sensitive
+- File upload logic duplicated in multiple places
+- BuildSection is highest risk area
+
+## Regression Checklist (Run After Each Slice)
+
+- Start new appeal
+- Save and exit
+- Resume saved appeal
+- Navigate sections
+- Upload file
+- View check answers
+- Submit appeal (if safe to test)
+- View confirmation page
+- Verify EN/CY parity
+
+Validation:
+
+- npm run lint passed
+- Playwright end-to-end new appeal journey passed
+- submission completed successfully through CRM insertion