feat(mock): in-process mock wallet — offline login + signing, no device

Promote the proven SSO/statement-store responder into a public, feature-gated
`mock_wallet` module (behind the `mock` feature; never in the default build).
`MockWalletPlatform` composes `truapi-platform`'s `MockPlatform` for the ten
platform-seam capabilities and answers `ChainProvider::connect` with a
`MockWalletConnection` that completes the SSO pairing handshake (login) and
answers signing requests over the statement-store channel — sr25519-signed and
P-256/AES-GCM-encrypted, exactly as a paired wallet would.

Closes the wallet-seam gap: login and signing now complete deterministically
in-process. Through-core tests cover login-to-authenticated and sign_payload.

Author: decrypto21

rust/crates/truapi-server/Cargo.toml

@@ -10,6 +10,9 @@ crate-type = ["rlib", "cdylib"]
 
 [features]
 default = []
+# Deterministic in-process mock wallet (dev/test only; never in the default
+# production WASM build). Pulls in truapi-platform's MockPlatform.
+mock = ["truapi-platform/mock"]
 
 [dependencies]
 truapi = { path = "../truapi" }

rust/crates/truapi-server/src/lib.rs

@@ -25,6 +25,12 @@ pub mod transport;
 #[cfg(test)]
 pub(crate) mod test_support;
 
+/// Deterministic in-process mock wallet (SSO/statement-store seam) composed with
+/// `truapi-platform`'s `MockPlatform`. Available in tests, or under the `mock`
+/// feature for out-of-crate consumers (browser E2E). Never in the default build.
+#[cfg(any(test, feature = "mock"))]
+pub mod mock_wallet;
+
 pub mod generated;
 
 #[cfg(target_arch = "wasm32")]