Merged PR 2260: refactor(representations): complete slice-based refactor of representations flow

## Representations Refactor — Behaviour-Preserving Structural Improvements

This PR delivers a full refactor of the representations flow, improving structure, readability, and maintainability while preserving all existing behaviour.

The work was completed using a controlled, slice-based approach with strict guardrails and regression validation at each step. No changes have been made to user journeys, payloads, routing, or EN/CY behaviour.

The result is a cleaner, more maintainable codebase with reduced coupling and clearer separation of concerns, ready for future enhancements without increased risk.

---

## What Was Done

The refactor was delivered incrementally across the following slices:

- **R1** — Representation entry logic extraction
- **R2** — Page loader separation (SSR/data orchestration)
- **R3** — Journey step resolution extraction
- **R4** — Flow shell decomposition
- **R5** — Representation elements normalisation
- **R6** — Data/service layer cleanup
- **R7** — Summary rendering proof slice
- **R8** — Submission/finalisation boundary isolation
- **R9** — Summary rollout (Batch 1)

Each slice:
- was isolated to a single concern
- followed strict guardrails
- was validated before merge

Full detail is available in:
`context/representations-refactor-tracker.md`

---

## Key Improvements

- Reduced coupling across the representations journey
- Separated data loading, orchestration, and rendering concerns
- Simplified complex conditional logic into testable helpers
- Standardised summary rendering using shared primitives (`SummaryCard`, `SummaryRow`)
- Isolated submission/finalisation sequencing into explicit boundaries
- Improved overall readability and maintainability

---

## Behaviour Preservation

This refactor does **not** change:

- User journeys (APP / IP / Agent / LPA)
- Route and query behaviour
- Payload contracts and API interactions
- Redux state shape and usage
- Validation rules and messaging
- EN/CY behaviour
- File upload / PDF / email sequencing
- Linked-case logic

All changes are structural only.

---

## Validation

### Automated

- `npm run lint` — passed (warnings only, no new errors)
- `npm run test:reps` — passed (7/7)

### Manual

Validated end-to-end across:

- APP
- IP
- Agent
- LPA

Including:

- representation creation
- editing/resuming representations
- submission flow
- confirmation/completion behaviour
- summary rendering across case types
- EN/CY parity

---

## Risk Management

The refactor targeted several high-risk areas:

- Case summary entry logic
- Representation submission/finalisation sequencing
- Dual-mode entry (new vs existing representation)

Risk was controlled through:

- small, incremental slices
- one branch per slice
- regression validation per slice
- strict behaviour-preservation guardrails
- controlled rollout for summary rendering changes

---

## Reviewer Guidance

Suggested areas to focus on:

- End-to-end representation journey (create → submit → complete)
- S...

tsconfig.json

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