feat: add Kotlin, Android, and KMP rules, agent, skills, and command

agents/kotlin-reviewer.md

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+---
+name: kotlin-reviewer
+description: Kotlin and Android/KMP code reviewer. Reviews Kotlin code for idiomatic patterns, coroutine safety, Compose best practices, clean architecture violations, and common Android pitfalls.
+tools: ["Read", "Grep", "Glob", "Bash"]
+model: sonnet
+---
+
+You are a senior Kotlin and Android/KMP code reviewer ensuring idiomatic, safe, and maintainable code.
+
+## Your Role
+
+- Review Kotlin code for idiomatic patterns and Android/KMP best practices
+- Detect coroutine misuse, Flow anti-patterns, and lifecycle bugs
+- Enforce clean architecture module boundaries
+- Identify Compose performance issues and recomposition traps
+- You DO NOT refactor or rewrite code — you report findings only
+
+## Workflow
+
+### Step 1: Gather Context
+
+Run `git diff --staged` and `git diff` to see changes. If no diff, check `git log --oneline -5`. Identify Kotlin/KTS files that changed.
+
+### Step 2: Understand Project Structure
+
+Check for:
+- `build.gradle.kts` or `settings.gradle.kts` to understand module layout
+- `CLAUDE.md` for project-specific conventions
+- Whether this is Android-only, KMP, or Compose Multiplatform
+
+### Step 3: Read and Review
+
+Read changed files fully. Apply the review checklist below, checking surrounding code for context.
+
+### Step 4: Report Findings
+
+Use the output format below. Only report issues with >80% confidence.
+
+## Review Checklist
+
+### Architecture (CRITICAL)
+
+- **Domain importing framework** — `domain` module must not import Android, Ktor, Room, or any framework
+- **Data layer leaking to UI** — Entities or DTOs exposed to presentation layer (must map to domain models)
+- **ViewModel business logic** — Complex logic belongs in UseCases, not ViewModels
+- **Circular dependencies** — Module A depends on B and B depends on A
+
+### Coroutines & Flows (HIGH)
+
+- **GlobalScope usage** — Must use structured scopes (`viewModelScope`, `coroutineScope`)
+- **Catching CancellationException** — Must rethrow or not catch; swallowing breaks cancellation
+- **Missing `withContext` for IO** — Database/network calls on `Dispatchers.Main`
+- **StateFlow with mutable state** — Using mutable collections inside StateFlow (must copy)
+- **Flow collection in `init {}`** — Should use `stateIn()` or launch in scope
+- **Missing `WhileSubscribed`** — `stateIn(scope, SharingStarted.Eagerly)` when `WhileSubscribed` is appropriate
+
+```kotlin
+// BAD — swallows cancellation
+try { fetchData() } catch (e: Exception) { log(e) }
+
+// GOOD — preserves cancellation
+try { fetchData() } catch (e: CancellationException) { throw e } catch (e: Exception) { log(e) }
+// or use runCatching and check
+```
+
+### Compose (HIGH)
+
+- **Unstable parameters** — Composables receiving mutable types cause unnecessary recomposition
+- **Side effects outside LaunchedEffect** — Network/DB calls must be in `LaunchedEffect` or ViewModel
+- **NavController passed deep** — Pass lambdas instead of `NavController` references
+- **Missing `key()` in LazyColumn** — Items without stable keys cause poor performance
+- **`remember` with missing keys** — Computation not recalculated when dependencies change
+- **Object allocation in parameters** — Creating objects inline causes recomposition
+
+```kotlin
+// BAD — new lambda every recomposition
+Button(onClick = { viewModel.doThing(item.id) })
+
+// GOOD — stable reference
+val onClick = remember(item.id) { { viewModel.doThing(item.id) } }
+Button(onClick = onClick)
+```
+
+### Kotlin Idioms (MEDIUM)
+
+- **`!!` usage** — Non-null assertion; prefer `?.`, `?:`, `requireNotNull`, or `checkNotNull`
+- **`var` where `val` works** — Prefer immutability
+- **Java-style patterns** — Static utility classes (use top-level functions), getters/setters (use properties)
+- **String concatenation** — Use string templates `"Hello $name"` instead of `"Hello " + name`
+- **`when` without exhaustive branches** — Sealed classes/interfaces should use exhaustive `when`
+- **Mutable collections exposed** — Return `List` not `MutableList` from public APIs
+
+### Android Specific (MEDIUM)
+
+- **Context leaks** — Storing `Activity` or `Fragment` references in singletons/ViewModels
+- **Missing ProGuard rules** — Serialized classes without `@Keep` or ProGuard rules
+- **Hardcoded strings** — User-facing strings not in `strings.xml` or Compose resources
+- **Missing lifecycle handling** — Collecting Flows in Activities without `repeatOnLifecycle`
+
+### Gradle & Build (LOW)
+
+- **Version catalog not used** — Hardcoded versions instead of `libs.versions.toml`
+- **Unnecessary dependencies** — Dependencies added but not used
+- **Missing KMP source sets** — Declaring `androidMain` code that could be `commonMain`
+
+## Output Format
+
+```
+[CRITICAL] Domain module imports Android framework
+File: domain/src/main/kotlin/com/app/domain/UserUseCase.kt:3
+Issue: `import android.content.Context` — domain must be pure Kotlin with no framework dependencies.
+Fix: Move Context-dependent logic to data or platforms layer. Pass data via repository interface.
+
+[HIGH] StateFlow holding mutable list
+File: presentation/src/main/kotlin/com/app/ui/ListViewModel.kt:25
+Issue: `_state.value.items.add(newItem)` mutates the list inside StateFlow — Compose won't detect the change.
+Fix: Use `_state.update { it.copy(items = it.items + newItem) }`
+```
+
+## Summary Format
+
+End every review with:
+
+```
+## Review Summary
+
+| Severity | Count | Status |
+|----------|-------|--------|
+| CRITICAL | 0     | pass   |
+| HIGH     | 1     | block  |
+| MEDIUM   | 2     | info   |
+| LOW      | 0     | note   |
+
+Verdict: BLOCK — HIGH issues must be fixed before merge.
+```
+
+## Approval Criteria
+
+- **Approve**: No CRITICAL or HIGH issues
+- **Block**: Any CRITICAL or HIGH issues — must fix before merge

commands/gradle-build.md

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+---
+description: Fix Gradle build errors for Android and KMP projects
+---
+
+# Gradle Build Fix
+
+Incrementally fix Gradle build and compilation errors for Android and Kotlin Multiplatform projects.
+
+## Step 1: Detect Build Configuration
+
+Identify the project type and run the appropriate build:
+
+| Indicator | Build Command |
+|-----------|---------------|
+| `build.gradle.kts` + `composeApp/` (KMP) | `./gradlew composeApp:compileKotlinMetadata 2>&1` |
+| `build.gradle.kts` + `app/` (Android) | `./gradlew app:compileDebugKotlin 2>&1` |
+| `settings.gradle.kts` with modules | `./gradlew assemble 2>&1` |
+| Detekt configured | `./gradlew detekt 2>&1` |
+
+Also check `gradle.properties` and `local.properties` for configuration.
+
+## Step 2: Parse and Group Errors
+
+1. Run the build command and capture output
+2. Separate Kotlin compilation errors from Gradle configuration errors
+3. Group by module and file path
+4. Sort: configuration errors first, then compilation errors by dependency order
+
+## Step 3: Fix Loop
+
+For each error:
+
+1. **Read the file** — Full context around the error line
+2. **Diagnose** — Common categories:
+   - Missing import or unresolved reference
+   - Type mismatch or incompatible types
+   - Missing dependency in `build.gradle.kts`
+   - Expect/actual mismatch (KMP)
+   - Compose compiler error
+3. **Fix minimally** — Smallest change that resolves the error
+4. **Re-run build** — Verify fix and check for new errors
+5. **Continue** — Move to next error
+
+## Step 4: Guardrails
+
+Stop and ask the user if:
+- Fix introduces more errors than it resolves
+- Same error persists after 3 attempts
+- Error requires adding new dependencies or changing module structure
+- Gradle sync itself fails (configuration-phase error)
+- Error is in generated code (Room, SQLDelight, KSP)
+
+## Step 5: Summary
+
+Report:
+- Errors fixed (module, file, description)
+- Errors remaining
+- New errors introduced (should be zero)
+- Suggested next steps
+
+## Common Gradle/KMP Fixes
+
+| Error | Fix |
+|-------|-----|
+| Unresolved reference in `commonMain` | Check if the dependency is in `commonMain.dependencies {}` |
+| Expect declaration without actual | Add `actual` implementation in each platform source set |
+| Compose compiler version mismatch | Align Kotlin and Compose compiler versions in `libs.versions.toml` |
+| Duplicate class | Check for conflicting dependencies with `./gradlew dependencies` |
+| KSP error | Run `./gradlew kspCommonMainKotlinMetadata` to regenerate |
+| Configuration cache issue | Check for non-serializable task inputs |

rules/kotlin/coding-style.md

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+---
+paths:
+  - "**/*.kt"
+  - "**/*.kts"
+---
+# Kotlin Coding Style
+
+> This file extends [common/coding-style.md](../common/coding-style.md) with Kotlin specific content.
+
+## Formatting
+
+- **ktlint** or **Detekt** for style enforcement
+- Official Kotlin code style (`kotlin.code.style=official` in `gradle.properties`)
+
+## Immutability
+
+- Prefer `val` over `var` — default to `val` and only use `var` when mutation is required
+- Use `data class` for value types; use immutable collections (`List`, `Map`, `Set`) in public APIs
+- Copy-on-write for state updates: `state.copy(field = newValue)`
+
+## Naming
+
+Follow Kotlin conventions:
+- `camelCase` for functions and properties
+- `PascalCase` for classes, interfaces, objects, and type aliases
+- `SCREAMING_SNAKE_CASE` for constants (`const val` or `@JvmStatic`)
+- Prefix interfaces with behavior, not `I`: `Clickable` not `IClickable`
+
+## Null Safety
+
+- Never use `!!` — prefer `?.`, `?:`, `requireNotNull()`, or `checkNotNull()`
+- Use `?.let {}` for scoped null-safe operations
+- Return nullable types from functions that can legitimately have no result
+
+```kotlin
+// BAD
+val name = user!!.name
+
+// GOOD
+val name = user?.name ?: "Unknown"
+val name = requireNotNull(user) { "User must be set before accessing name" }.name
+```
+
+## Sealed Types
+
+Use sealed classes/interfaces to model closed state hierarchies:
+
+```kotlin
+sealed interface UiState<out T> {
+    data object Loading : UiState<Nothing>
+    data class Success<T>(val data: T) : UiState<T>
+    data class Error(val message: String) : UiState<Nothing>
+}
+```
+
+Always use exhaustive `when` with sealed types — no `else` branch.
+
+## Extension Functions
+
+Use extension functions for utility operations, but keep them discoverable:
+- Place in a file named after the receiver type (`StringExt.kt`, `FlowExt.kt`)
+- Keep scope limited — don't add extensions to `Any` or overly generic types
+
+## Scope Functions
+
+Use the right scope function:
+- `let` — null check + transform: `user?.let { greet(it) }`
+- `run` — compute a result using receiver: `service.run { fetch(config) }`
+- `apply` — configure an object: `builder.apply { timeout = 30 }`
+- `also` — side effects: `result.also { log(it) }`
+- Avoid deep nesting of scope functions (max 2 levels)
+
+## Error Handling
+
+- Use `Result<T>` or custom sealed types
+- Use `runCatching {}` for wrapping throwable code
+- Never catch `CancellationException` — always rethrow it
+- Avoid `try-catch` for control flow
+
+```kotlin
+// BAD — using exceptions for control flow
+val user = try { repository.getUser(id) } catch (e: NotFoundException) { null }
+
+// GOOD — nullable return
+val user: User? = repository.findUser(id)
+```