feat(data): add Conversation, Session, Message data classes

[ilmoniemi]

User Story

As a mobile-app engineer, I want the core Conversation / Session / Message data classes defined so that subsequent tickets (repository interface, fake repository, UI state) have a typed schema to build against.

Context

Foundational Phase 1 scaffolding. Mirrors the schema that pyrycode CLI's conversations.json (Phase 3) and Discord-side (Phase 2) will share — same entity shape across all consumers. The data/ package does not yet exist in the repo; this ticket creates it.

Per repo CLAUDE.md (Don't section): the data layer must stay portable (Compose Multiplatform is a walk-back trigger). See Technical Notes.

Spec

// app/src/main/java/de/pyryco/mobile/data/model/

data class Conversation(
    val id: String,
    val name: String?,             // null for discussions; user-set for channels
    val cwd: String,
    val currentSessionId: String,
    val sessionHistory: List<String>,
    val isPromoted: Boolean,       // false = discussion, true = channel
    val lastUsedAt: Instant,
)

data class Session(
    val id: String,
    val conversationId: String,
    val claudeSessionUuid: String,
    val startedAt: Instant,
    val endedAt: Instant?,
)

data class Message(
    val id: String,
    val sessionId: String,
    val role: Role,
    val content: String,
    val timestamp: Instant,
    val isStreaming: Boolean,
)

enum class Role { User, Assistant, Tool }

Acceptance Criteria

• Conversation, Session, Message, and Role are declared in package de.pyryco.mobile.data.model with the exact field names, types, and nullability shown in the Spec.
• A unit test for each of the three data class types asserts that two instances with identical fields are equals, that hashCode matches, and that copy() produces a new instance with the requested field overridden and all others preserved.
• A unit test asserts that Role has exactly the values User, Assistant, Tool (e.g. via Role.values().toList()).
• ./gradlew assembleDebug passes.
• ./gradlew test passes.

Technical Notes

• Use kotlinx.datetime.Instant, not java.time.Instant — CLAUDE.md requires the data layer to remain portable for a potential Compose Multiplatform walk-back. The version catalog (gradle/libs.versions.toml) does not yet declare kotlinx-datetime; the architect should add it.
• File layout (one-class-per-file vs. co-locating Role in Message.kt) is an architect call — the AC fixes the package and the type shapes, not the file count.

Out of Scope

• ConversationRepository interface and FakeConversationRepository (next ticket).
• Persistence (DataStore / Room).
• Serialization for the Phase 4 wire protocol — these types stay annotation-free for now.

Size Estimate

XS — ~40 lines of production code (4 small declarations in one package), plus paired unit tests. No cross-package coordination; no consumers wired in this ticket.

[ilmoniemi]

🤖 Product Owner — creates structured issues

po agent has completed work on this ticket.

Agent output (click to expand)

Refined #2 in place. Kept the spec block verbatim, reframed "Goal" → User Story + Context, tightened the equality/copy AC into a concrete assertion shape, split out the `Role` enum check as its own AC (the original lumped it under "data class equality" which doesn't apply to enums), and removed the "all four files" structural prescription. Added a Technical Notes block flagging `kotlinx.datetime.Instant` per CLAUDE.md's portability rule. Size stays XS; not security-sensitive. Dispatcher will add `ready:po` on completion.

Ready for human review. Move to the next column when approved.

[ilmoniemi]

🤖 System Architect — defines Go interfaces, data flows, concurrency patterns

architect agent has completed work on this ticket.

Agent output (click to expand)

Spec committed. Summary:

- **Size:** XS confirmed — 3 data classes + 1 enum, ~40 production lines, new files only, no edit fan-out, no in-flight branch overlap.
- **File layout:** 3 source files (`Conversation.kt`, `Session.kt`, `Message.kt` co-locating `Role`) + 3 test files mirroring layout.
- **Dependency:** `kotlinx-datetime 0.6.2` wired via version catalog (`libs.versions.toml` + `app/build.gradle.kts`), explicitly chosen over `java.time.Instant` per CLAUDE.md's Compose Multiplatform walk-back.
- **Tests:** JUnit 4 idiom matching `ExampleUnitTest.kt`; deterministic `Instant.fromEpochSeconds(0)` fixtures.

Ready for human review. Move to the next column when approved.