[PM-27135] feat: Add Use Passkey screen

[morganzellers-bw]

🎟️ Tracking

PM-27135

📔 Objective

Third PR in a 4-PR stack adding SDK-backed passkey test scenarios to TestHarness. Stacked on #2946.

• Adds the "Use Passkey (SDK)" scenario: lists credentials registered via SDKPasskeyService.registeredCredentials, and asserts against the tapped credential's specific credential ID and relying party ID via SDKPasskeyService.assertPasskey, showing the resulting relying party ID and username.
• Wires the new screen into the scenario picker and root navigation.

📸 Screenshots

---

Stack: #2945 → #2946 → #2947 → #2948

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

Re-reviewed the third PR in the TestHarness passkey stack after the SDK* type prefixes were dropped. The change adds the "Use Passkey" screen (Action/Effect/State/Processor/View plus processor tests and a GetAssertionResult fixture) and wires it into RootRoute, RootCoordinator, and the scenario picker. Structure, Localizations keys (all present in Localizable.strings for SwiftGen), fixture placement under Fixtures/ (excluded from the app target and included in the test target by project-bwth.yml), preview #if DEBUG gating, and test setup/teardown all mirror the sibling RegisterPasskey screen; Data.asHexString() resolves to the public BitwardenKit extension. No security concerns: this is a separate TestHarness target, no production code is touched, crypto stays behind PasskeyService/BitwardenSdk, and the synthetic identity remains keychain-backed.

Code Review Details

• ⚠️ : Empty state renders while credentials are still loading, showing "No credentials registered yet" before the list arrives (existing unresolved thread — not re-posted)
  • TestHarnessShared/UI/Autofill/Passkey/UsePasskeyView.swift:40

PR Metadata Assessment

• ❓ QUESTION: This adds a new user-facing screen but the Screenshots section is still an HTML-comment placeholder, so it renders empty. Please add screenshots before merge as the description asks.

[claude]

⚠️ IMPORTANT: The empty state renders while credentials are still loading, so testers see "No credentials registered yet" before the real list arrives.

Details and fix

registeredCredentials starts [] and status starts .idle, so SwiftUI evaluates body and shows the empty-state message before .task { await store.perform(.loadRegisteredCredentials) } completes. That load is not cheap on the first call — DefaultSDKPasskeyService.session() hits the keychain and then runs initializeUserCrypto with 600,000 PBKDF2 iterations — so the misleading "Use Register Passkey (SDK) to create one" message is visible for a noticeable moment even when credentials do exist. For a harness screen whose whole job is to list registered credentials, that can read as a registration failure.

Distinguishing "not loaded yet" from "loaded and empty" fixes it, e.g. add a loading flag to the state:

// SDKUsePasskeyState
var isLoadingCredentials = true

// SDKUsePasskeyProcessor.loadRegisteredCredentials()
defer { state.isLoadingCredentials = false }

// SDKUsePasskeyView.registeredCredentialsSection
if store.state.isLoadingCredentials {
    ProgressView()
} else if store.state.registeredCredentials.isEmpty {
    Text(Localizations.sdkNoRegisteredCredentials)
        .foregroundStyle(.secondary)
} else {
    // ...
}

This also covers the tap path: .disabled(store.state.status == .inProgress) silently disables the rows during an assertion with no visible indicator, unlike SDKRegisterPasskeyView, which shows a ProgressView next to its button.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.47%. Comparing base (3d55e64) to head (9f46c09).

Additional details and impacted files

@@                              Coverage Diff                              @@
##           pm-27134-testharness-register-passkeys-ui    #2947      +/-   ##
=============================================================================
- Coverage                                      79.48%   79.47%   -0.01%     
=============================================================================
  Files                                           1172     1172              
  Lines                                          75144    75144              
=============================================================================
- Hits                                           59726    59724       -2     
- Misses                                         15418    15420       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.