Comprehensive Unit Testing and small Core Logic Refactoring

[pzauner]

This PR introduces a robust testing framework and significantly improves the reliability of the keyboard's core logic, focusing on modifier states, input context detection, and the suggestion engine.

Test Infrastructure

• Robolectric Integration: Added Robolectric to gradle/libs.versions.toml and app/build.gradle.kts. This allows running Unit Tests that depend on Android framework classes (like KeyEvent, EditorInfo, and InputType) directly on the JVM.

New Unit Tests

Implemented a comprehensive suite of tests to prevent regressions in core features:

• ModifierStateControllerTest: Validates the Shift/Caps-Lock state machine, including double-tap detection, one-shot shift consumption, and state persistence.
• InputContextStateTest: Ensures correct detection of field types (Password, Email, URI) and respects Android IME flags (CAP_SENTENCES, CAP_WORDS, CAP_CHARACTERS).
• SuggestionEngineTest and SymSpellTest: Verifies the accuracy of word corrections and the suggestion generation logic.
• DictionaryRepositoryTest: Tests dictionary loading and lookup performance, supported by a new FakeDictionaryRepository for isolated testing.
• CurrentWordTrackerTest: Validates how the IME tracks the current word during typing and cursor movements.
• CasingHelperTest and PunctuationTest: Ensures correct behavior for auto-capitalization and punctuation handling across different languages.

Core Logic Improvements

This is the only place where the actual structure of the codebase was modified. This was performed for two reasons:

a) To enable testing in the first place. Testing private methods via reflection is problematic in Kotlin when the class performs strict null-checks on its constructor dependencies (such as DictionaryRepository). Moving the pure logic into a companion object allows for clean unit tests without requiring complex mocks.

b) The splitApostropheWord method was hard-capped to prefixes of at most 3 characters (e.g., l', un', all'). This caused longer Italian elisions like dell' or nell' to be bypassed by the specialized correction logic."

• AutoReplaceController: Refactored the auto-replace logic to better handle elisions (e.g., Italian "l'amico") and improved the integration with the dictionary repository.
• DictionaryRepository: Optimized asynchronous loading and memory management for dictionaries.
• InputContextState: Enhanced the mapping of EditorInfo to internal state flags, providing more granular control over features like auto-capitalization and suggestions based on the active input field.

Change Stats

• Files changed: 16
• Insertions: ~1160 lines (primarily test coverage)
• Status: All unit tests are passing (./gradlew testDebugUnitTest).