feat(trezor): add FirmwareError and DeviceLocked TrezorException variants

[piotr-iohk]

Problem

Native apps still classify some Trezor failures outside the typed TrezorException hierarchy:

1. Firmware faults (protocol code 99) — Android matches message substrings such as "Device error (code 99)" and "Firmware error" in TrezorExceptionExt.kt. This is fragile and duplicates logic core already owns in src/modules/trezor/errors.rs, where DeviceError::DeviceError { code, message } is currently mapped to generic TrezorError::DeviceError.

2. Locked device — Android detects pinProtection == true && unlocked == false from TrezorFeatures in TrezorRepo.requireUnlocked() and synthesizes TrezorException.DeviceBusy(). That conflates two distinct UX states:

   • Device locked → unlock guidance
   • Device busy → wait / reconnect guidance

iOS has similar string-based handling in TrezorManager.swift.

Consumer-side heuristics are easy to break when error copy changes and force both apps to maintain parallel classification logic.

Proposed change

Extend the exported TrezorError / TrezorException enum in src/modules/trezor/errors.rs:

FirmwareError

Map Trezor protocol failure code 99 (Failure_FirmwareError) to a dedicated variant instead of generic DeviceError.

• Preserve error_details for diagnostics.
• Update test_failure_code_unknown_stays_generic_device_error in src/modules/trezor/tests.rs — that test currently asserts code 99 stays generic; it should assert FirmwareError instead.

DeviceLocked

Add a distinct variant for “device has PIN protection and is currently locked”.

Options (pick one in implementation):

• Map from an existing trezor-connect-rs signal if available at connect/features refresh time.
• Or expose locked state explicitly when get_features() reports pin_protection && !unlocked before an operation proceeds, returning DeviceLocked instead of requiring apps to reimplement the rule.

Keep DeviceBusy for transport/session contention only. Do not overload it for locked state.

Regenerate UniFFI bindings after the enum change.

Tests

• Code 99 device failure maps to TrezorError::FirmwareError (not generic DeviceError).
• Unrelated device error codes still map to DeviceError.
• Locked-device path returns DeviceLocked and is distinct from DeviceBusy.
• Existing DeviceBusy transport mapping tests remain unchanged.

Acceptance criteria

• FFI exposes TrezorException.FirmwareError and TrezorException.DeviceLocked.
• No message-string sniffing required in native apps for these two cases.
• Rust tests, Clippy, and formatting pass.
• Bindings published in a core release.

Consumer follow-up

After release, update bitkit-android and bitkit-ios:

1. Remove isTrezorFirmwareError() message heuristics; match TrezorException.FirmwareError.
2. Remove requireUnlocked() → DeviceBusy synthesis; match TrezorException.DeviceLocked.
3. Keep UX mapping:
   • DeviceLocked → unlock info toast
   • FirmwareError → reconnect-hardware toast
   • DeviceBusy → busy / backoff guidance

Related

• fix: polish trezor reliability and ux bitkit-android#1067 — Corey review follow-up
• fix: polish trezor reliability and ux bitkit-ios#621
• Prior art: fix(onchain): return canonical txid for already-known raw broadcasts #123 moved broadcast txid recovery into core instead of app string matching

Priority

Medium — not blocking v1 Trezor ship; apps have working heuristics. Reduces long-term fragility as more Trezor flows are added.