feat: mock platform

[decrypto21]

Summary

Adds a mock host that swaps the platform seam while running the real Rust core. Tests and demos exercise the actual truapi-server dispatcher, account management, permission service, signing orchestration, and SCALE wire — with device/wallet capabilities supplied by an in-memory, config-driven double instead of a real device or paired wallet.

Why "swap the seam, keep the core"

TrUAPI is one core with two seams: the platform seam (truapi-platform capability traits — the OS/device primitives the core delegates) and the wallet seam (keys in a paired wallet over SSO). The mock replaces only the platform seam. Because every request still flows through the real core, the mock is faithful by construction — it can't drift from real host semantics the way a hand-rolled fake would.

What this delivers

truapi-platform — MockPlatform (behind the mock feature, dev-only)

• MockConfig drives behavior: permission policies (AllowAll / DenyAll), chain behaviors (Silent / Scripted / Closed / ConnectError), confirmation control (ConfirmKind), and fault injection (MockFaults: storage / navigation / preimage / …).
• Implements every capability trait (ProductStorage, CoreStorage, Navigation, Notifications, Permissions, Features, ChainProvider / JsonRpcConnection, AuthPresenter, UserConfirmation, ThemeHost, PreimageHost) against the core's async_trait surface and truapi::latest types.

truapi-server — through-core proof

• Tests build the real core from a MockPlatform and assert on the SCALE wire envelopes the dispatcher emits: feature-support dispatch, storage round-trip, device-permission policy (DenyAll → granted: false), preimage confirm-gate, and storage-fault surfacing.

truapi-host-wasm — createMockHost

• In-memory HostCallbacks for browser / Web Worker host tests, a headless WASM-bridge test, and CI wiring.

Proven, not asserted

The mock is validated through the real core, never in isolation: the truapi-server tests decode the dispatcher's actual wire output, so a mock that diverged from real host semantics would fail them.

Scope & safety

• The mock feature is a dev-dependency only — it never enters the default (production WASM) build.
• No change to real host behavior or the protocol surface.

Stacked on

#104 (Rust-core port). This branch rebases onto #104's current head — review / merge #104 first.

Status

Area	State
truapi-platform (MockPlatform)	✅ green — 22 mock unit tests, clippy/fmt clean
truapi-server (through-core)	✅ green — 214 tests incl. 5 through-core
truapi-host-wasm (createMockHost)	🚧 finalizing against #104's reworked worker callbacks + WASM rebuild

Test plan

cargo test -p truapi-platform --features mock
cargo test -p truapi-server --lib
cargo clippy --workspace --all-targets --all-features -- -D warnings
cargo +nightly fmt --check

Tracking

Roadmap and follow-ups under #257.