Apply a WAL to Reconstruct State (Practical)

Question

## Problem

Neon separates compute from storage; pages are reconstructed from a write-ahead log. Given a base page and a list of WAL records, apply them in LSN order to reconstruct the current page.

## Example
```
base + [insert, update, delete] in LSN order -> current page
```

## Constraints
- Apply in order; support point-in-time (stop at an LSN)

## What Neon looks for
Grounded in Neon's storage engine: WAL replay and time-travel by stopping at an LSN.