core: implement domain model and newtypes (T0.2)

PROGRESS.md

@@ -0,0 +1,27 @@
+# PROGRESS.md
+
+## T0.2 — Domain model + newtypes
+
+**Status:** Complete
+
+**What was done:**
+- Created `crates/cockpit-core/src/model.rs` with all domain types from SPEC.md §6.
+- Newtypes: `ReviewId`, `IssueRef`, `PrRef`, `CommentId`, `ProjectRef` — all distinct types
+  wrapping `String`, with `new()`, `as_str()`, and `Display`.
+- Enums: `GateState`, `AgentMode`, `CommentOrigin`, `Anchor`, `Artifact`.
+- Structs: `PlanStep`, `PlanDoc`, `DiffData`, `Comment`, `AgentRun`, `ProjectPlan`, `Review`.
+- Wired `pub mod model;` in `lib.rs`.
+
+**Test results:**
+- 7 tests pass (6 new in model + 1 existing smoke).
+- `cargo fmt` clean, `cargo clippy -- -D warnings` clean, `cargo test --all` green.
+
+**Decisions:**
+- Used `SystemTime` instead of `Instant` for `AgentRun.started_at` because `Instant` is not
+  serializable and has no cross-process meaning. Documented inline.
+- `stale: bool` on `Review` kept as boolean per SPEC.md §6 — it is genuinely binary (an
+  ancestor is or is not in rework) and the spec is explicit.
+- `DiffData` is a placeholder with `raw: String` — will be fleshed out in T0.5/T4.3.
+- Deferred `uuid` dependency for ID generation to the task that first needs runtime IDs.
+- Used a `newtype_id!` macro for the five ID types since they are structurally identical.
+- Added `Eq` to all types whose fields support it, per CLAUDE.md §2 "derive eagerly."

crates/cockpit-core/src/lib.rs

@@ -9,8 +9,9 @@
 /// Crate version, surfaced for diagnostics.
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");
 
+pub mod model;
+
 // Modules land here as the plan progresses:
-//   pub mod model;       // T0.2 — domain types + newtypes
 //   pub mod gate;        // T0.3 — the Gated trait + state machine
 //   pub mod adapters;    // T0.4–T0.6 — linear, github, git, agent
 //   pub mod prompt;      // T1.1 — deterministic prompt assembly