GT-2783 Convert the login flow to a Circuit LoginScreen

[smgoss]

Resolves #4610 (GT-2783)

Login was still hosted by its own Activity (LoginActivity hosting a stateful LoginLayout). This converts it to a Circuit screen launched with startCircuitActivity, following the same structure as the Delete Account conversion (DeleteAccountScreen/DeleteAccountPresenter/DeleteAccountLayout).

Changes

• LoginScreen: @Parcelize data class LoginScreen(val createAccount: Boolean = false) : ParcelableScreen.
• LoginPresenter: nested UiState (createAccount, loginError) and UiEvent (Login(AccountType), ClearError, Close), plain @AssistedFactory @CircuitInject factory. It owns the login error state (still rememberSaveable) and a small CloseWhenAuthenticated() helper that pops the navigator once GodToolsAccountManager.isAuthenticatedFlow reports an authenticated account. That covers both a successful login and opening the screen while already logged in. Close pops the navigator.
• LoginLauncherProducer: the login launcher registers Activity result callbacks from a composable, so it can't be mocked with plain mockk. Following the ToolFiltersStateProducer pattern, it is an interface with DefaultLoginLauncherProducer (a thin wrapper around the existing rememberLoginLauncher, so Google and Facebook still go through the account-manager abstraction), bound in a new LoginModule, plus a hand-written FakeLoginLauncherProducer for tests.
• LoginLayout: now a stateless @CircuitInject UI taking (state: UiState, modifier: Modifier = Modifier) that sends UiEvents. TEST_TAG_* constants were added. The visuals are unchanged.
• DrawerMenuLayout: the Login and Create Account actions call context.startCircuitActivity(LoginScreen(...)).
• Removed LoginActivity, startLoginActivity() and the .ui.login.LoginActivity manifest entry in the switch commit. Removed LoginLayoutEvent and the temporary stateful LoginLayout overload (kept only so commit 1 compiles) in a separate orphan commit.

Commits: 1) add the Circuit screen with tests, 2) switch callers and delete LoginActivity, 3) remove orphaned code.

Behavior change to be aware of: LoginResponse.Success no longer closes the screen directly. The screen closes when the account manager reports the authenticated account. Both providers store the user id on success, so isAuthenticatedFlow flips right away. This avoids popping twice (the old Activity called finish() twice, which did nothing extra, but a double pop() would also pop the previous screen if LoginScreen is ever pushed onto an existing back stack).

Intentionally not done:

• The account providers are unchanged. The Credential Manager migration for Google auth is tracked separately in Migrate Google authentication to Android Credential Manager #4612.
• The existing GT_BLUE background, FACEBOOK_BLUE color and null content descriptions in the layout were kept as they were, so this PR has no visual changes.
• No coordination change with GT-3107 Convert AccountLayout to Circuit #4592 (on hold). This PR only changes the two login onClick lines in DrawerMenuLayout.

Tests

• LoginPresenterTest (src/test): createAccount is passed through to state and to the launcher; a login error shows in loginError; a successful login shows no error; the screen pops once authenticated and when already authenticated; Login launches Google and Facebook; ClearError dismisses the error; Close pops.
• LoginLayoutTest (testDebug, v2.runComposeUiTest): heading for login vs create account, close icon, Google and Facebook buttons, and the error dialog (hidden, shown, confirm fires ClearError).
• LoginLayoutPaparazziTest: Login, Create Account and Error scenarios. Goldens are not recorded yet; run the Record Snapshots workflow on this branch and fold the result into the first commit.
• Not compiled or run locally: Gradle can't reach its Maven repositories in the environment where this was written. Imports, signatures and test helpers were checked by hand against sibling code. Please run ./gradlew :build-logic:ktlintCheck ktlintCheck, ./gradlew :app:testProductionDebugUnitTest and verifyPaparazzi (after recording) in CI.

Review

Checked against the project conventions for Circuit, migration and testing, a correctness review, a security review and a simplification pass. Nothing needed changing.

• Architecture: the full LoginScreen/LoginPresenter/LoginLayout file set is present. The screen is @Parcelize data class ... : ParcelableScreen. The presenter has a plain nested @AssistedFactory @CircuitInject Factory, and present() stays short. LoginLauncherProducer follows the interface + Default* + @Binds + Fake* pattern, and LoginModule sits in the feature package. The drawer uses startCircuitActivity. The switch commit and the orphan-removal commit are separate. LoginLayoutPaparazziTest is present.
• No references remain to LoginActivity, startLoginActivity or LoginLayoutEvent in code or manifests. rememberLoginLauncher falls back to the Hilt entry point, so it works inside CircuitActivity.
• Security: no findings. CircuitActivity was already exported, and LoginScreen gives no new privilege.
• Left as is on purpose: Success doesn't pop directly, to avoid a double pop. Both providers write the user id before reporting Success. The close icon's null contentDescription existed before and is kept to avoid visual changes. Using rememberUpdatedState(state.eventSink) matches the owners' pattern.
• Still open: Paparazzi goldens must be recorded by the CI workflow. Nothing has been compiled yet.
• Merges cleanly with Migrate Google authentication to Android Credential Manager #4612: no overlapping files and no merge-tree conflicts.

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Generated by Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 83.60656% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.59%. Comparing base (88bef9f) to head (8f1e3c8).

Files with missing lines	Patch %	Lines
...org/cru/godtools/ui/login/LoginLauncherProducer.kt	0.00%	4 Missing ⚠️
...lin/org/cru/godtools/ui/drawer/DrawerMenuLayout.kt	0.00%	2 Missing ⚠️
...in/kotlin/org/cru/godtools/ui/login/LoginLayout.kt	90.90%	0 Missing and 2 partials ⚠️
...in/kotlin/org/cru/godtools/ui/login/LoginModule.kt	0.00%	1 Missing ⚠️
...kotlin/org/cru/godtools/ui/login/LoginPresenter.kt	96.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4654      +/-   ##
===========================================
+ Coverage    53.56%   54.59%   +1.02%     
===========================================
  Files          440      442       +2     
  Lines        11572    11590      +18     
  Branches      1944     1946       +2     
===========================================
+ Hits          6198     6327     +129     
+ Misses        4790     4675     -115     
- Partials       584      588       +4     

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