[fern-replay] Initialize Replay for SDK customizations (#899)

## Replay Initialization

This PR initializes [Fern Replay](https://buildwithfern.com) for this
SDK repository.
Replay automatically preserves your customizations across SDK
regenerations.

**Base generation commit:** `e0c9925`

Clean start — no historical patches imported. Future customizations will
be tracked automatically.

---
Once merged, your customizations will be automatically preserved on
future `fern generate` runs.

Co-authored-by: fern-api[bot] <115122769+fern-api[bot]@users.noreply.github.com>

Author: fern-api[bot]