Merge branch 'feature/issue-ticket-system' into feature/background-tasks-first-class

Intègre le système de tickets/issues V1 (validé QA vert de bout en bout,
mémoire tickets-v1-e2e-validated-qa) dans la branche des tâches de fond.
Conflits résolus : app-tauri/state.rs, domain/events.rs, domain/lib.rs, domain/ports.rs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/domain/src/ports.rs

@@ -33,6 +33,9 @@ use crate::background_task::{
 };
 use crate::events::DomainEvent;
 use crate::ids::{AgentId, NodeId, ProjectId, ScheduleId, SessionId, TaskId};
+use crate::issue::{
+    Issue, IssueCarnet, IssueIndexEntry, IssueListFilter, IssueNumber, IssueRef, IssueVersion,
+};
 use crate::markdown::MarkdownDoc;
 use crate::memory::{Memory, MemoryIndexEntry, MemoryLink, MemorySlug};
 use crate::permission::ProjectPermissions;
@@ -566,6 +569,27 @@ pub enum WakeError {
     Task(String),
 }
 
+/// Errors from the issue store.
+#[derive(Debug, Clone, PartialEq, Eq, Error)]
+pub enum IssueStoreError {
+    /// The requested issue does not exist.
+    #[error("issue not found")]
+    NotFound,
+    /// Optimistic concurrency conflict.
+    #[error("issue version conflict: expected {expected}, actual {actual}")]
+    VersionConflict {
+        /// Expected version.
+        expected: IssueVersion,
+        /// Actual persisted version.
+        actual: IssueVersion,
+    },
+    /// The issue payload is invalid.
+    #[error("issue invalid: {0}")]
+    Invalid(String),
+    /// Store I/O or serialization failed.
+    #[error("issue store failed: {0}")]
+    Store(String),
+}
 // ---------------------------------------------------------------------------
 // Git port support types
 // ---------------------------------------------------------------------------
@@ -1385,6 +1409,84 @@ pub trait AgentWakePort: Send + Sync {
     ) -> Result<(), WakeError>;
 }
 
+/// Allocates monotonic per-project issue numbers.
+#[async_trait]
+pub trait IssueNumberAllocator: Send + Sync {
+    /// Allocates the next number for `root`.
+    ///
+    /// Implementations must never reuse an allocated number, even if a later
+    /// issue creation step fails.
+    ///
+    /// # Errors
+    /// [`IssueStoreError`] on persistence/lock failure.
+    async fn allocate_next(&self, root: &ProjectPath) -> Result<IssueNumber, IssueStoreError>;
+}
+
+/// Persistence port for project-scoped issues.
+#[async_trait]
+pub trait IssueStore: Send + Sync {
+    /// Creates a new issue.
+    ///
+    /// # Errors
+    /// [`IssueStoreError`] when the issue already exists or cannot be stored.
+    async fn create(&self, root: &ProjectPath, issue: &Issue) -> Result<(), IssueStoreError>;
+
+    /// Reads an issue by `#N` reference.
+    ///
+    /// # Errors
+    /// [`IssueStoreError::NotFound`] when absent.
+    async fn get_by_ref(
+        &self,
+        root: &ProjectPath,
+        issue_ref: IssueRef,
+    ) -> Result<Issue, IssueStoreError>;
+
+    /// Lists issue index entries matching `filter`.
+    ///
+    /// # Errors
+    /// [`IssueStoreError`] on persistence failure.
+    async fn list(
+        &self,
+        root: &ProjectPath,
+        filter: IssueListFilter,
+    ) -> Result<Vec<IssueIndexEntry>, IssueStoreError>;
+
+    /// Replaces an issue after checking its expected version.
+    ///
+    /// # Errors
+    /// [`IssueStoreError::VersionConflict`] on optimistic-concurrency conflict.
+    async fn update(
+        &self,
+        root: &ProjectPath,
+        issue: &Issue,
+        expected_version: IssueVersion,
+    ) -> Result<(), IssueStoreError>;
+
+    /// Reads only the issue carnet projection.
+    ///
+    /// # Errors
+    /// [`IssueStoreError::NotFound`] when absent.
+    async fn read_carnet(
+        &self,
+        root: &ProjectPath,
+        issue_ref: IssueRef,
+    ) -> Result<IssueCarnet, IssueStoreError>;
+
+    /// Replaces an issue carnet and increments the issue version.
+    ///
+    /// # Errors
+    /// [`IssueStoreError::VersionConflict`] on optimistic-concurrency conflict.
+    async fn write_carnet(
+        &self,
+        root: &ProjectPath,
+        issue_ref: IssueRef,
+        carnet: MarkdownDoc,
+        actor: crate::issue::IssueActor,
+        now_ms: u64,
+        expected_version: IssueVersion,
+    ) -> Result<IssueCarnet, IssueStoreError>;
+}
+
 /// Git operations for a project. Named `GitPort` to avoid clashing with the
 /// [`crate::git::GitRepository`] *entity* (state image).
 #[async_trait]