feat(core): rename stampers and expose them on createZeroDevWallet

[andrascodes]

This PR is part of a stack created with Aviator. feat(expo-example): configure and add magic link login #142 fix(expo-example): add EAS local build config and fix HMR bug with secureStoreStamper #141 feat(expo-example): migrate to expo-router #131 feat(react): enable OAuth in React Native #80 feat(expo-example): add Passkey auth and test on Android #124 feat: add expo-example app #76 fix(react): race condition between initialize and isAuthorized in RN #75 feat: add fetchOptions to core and react so Origin header can be sent on RN #74 feat(react): expose stamper, storage and shouldInit params #73 refactor(core): use atob and btoa instead of Buffer #72 ➡️ feat(core): rename stampers and expose them on createZeroDevWallet #71 main

Closes FS-1925, FS-1946

Renamed the stampers to a more generic name apiKeyStamper and passkeyStampers. Exposed them so they can be passed in through createZeroDevWallet(). But I haven't removed the default indexedDbStamper and webauthnStamper so this is not a breaking change.

(will add more documentation later)

[SahilVasava]

Reviewed. The architectural direction is right — moving stampers to injected dependencies and the prepare/commit key rotation API is a clear improvement. Comments are mostly about consistency follow-through:

• The StamperType rename is half-finished; doing it atomically here avoids the // TODO: @stamper-type markers landing in main.
• publicKey field tightening surfaced a pre-existing weakness in the OAuth path (non-blocking).
• Misc nits on docstrings.

Approve conceptually, just want the rename consistency before merge.

[SahilVasava]

LGTM — all prior review comments addressed (StamperType renamed to 'apiKey' | 'passkey', OAuth path now fails loud on missing public key, parseSession deduped to single token field, docstrings clarified).