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

.clinerules/default-rules.md

@@ -0,0 +1,95 @@
+# Default Rules (Reference Only)
+
+## Important
+
+This file is **not the active rule set for this refactor branch**.
+
+Active working rules are defined in:
+
+- `.clinerules/refactor-branch-rules.md`
+- `context/refactor-branch-charter.md`
+- `context/newappeal-refactor-guardrails.md`
+
+Do not load this file by default.
+
+---
+
+## Purpose
+
+This file provides general repository-wide guidance and may be referenced when needed for broader context.
+
+---
+
+## Repository Mission
+
+Deliver safe, accessible, bilingual (EN/CY), and reliable public-service functionality without regressing core journeys.
+
+---
+
+## General Priorities
+
+1. Safety and security of user data
+2. Stability of public-facing journeys
+3. Accessibility and bilingual parity
+4. Maintainability of code
+5. Controlled, safe delivery
+
+---
+
+## General Coding Guidance
+
+- Follow existing repo patterns
+- Keep page-level logic thin
+- Move reusable logic into `components/`, `actions/`, or `lib/`
+- Avoid broad refactors in feature or bugfix work
+- Prefer small, focused changes
+
+---
+
+## Architecture Guardrails (General)
+
+- Do not bypass auth/session handling
+- Do not weaken security controls
+- Preserve relay request integrity
+- Maintain EN/CY route parity
+- Keep Redux hydration/persistence stable
+
+---
+
+## Validation Expectations (General)
+
+- linting must pass
+- user-facing changes must be verified
+- accessibility and EN/CY checks required
+- sensitive flows require negative-path checks
+
+---
+
+## When To Use This File
+
+Only reference this file when:
+
+- broader repository rules are required
+- behaviour conflicts are unclear
+- no branch-specific guidance exists
+
+---
+
+## Summary
+
+This file is background guidance only.
+
+For this refactor branch:
+
+- follow branch-specific rules first
+- prioritise behaviour preservation
+- keep context minimal and focused
+
+## Branching Guidance (Reference)
+
+Branching depends on work type:
+
+- BAU work typically branches from `SIPS-Development`
+- refactor-stream work for the new appeal flow uses `refactor` as the base branch
+
+Follow branch-specific rules first.