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/events.rs

@@ -1,7 +1,8 @@
 //! Domain events published on the [`crate::ports::EventBus`] and relayed to the
 //! presentation layer (ARCHITECTURE §3.2).
 
-use crate::ids::{AgentId, ProfileId, ProjectId, SessionId, SkillId, TaskId, TemplateId};
+use crate::ids::{AgentId, IssueId, ProfileId, ProjectId, SessionId, SkillId, TaskId, TemplateId};
+use crate::issue::{IssueLinkKind, IssuePriority, IssueRef, IssueStatus, IssueVersion};
 use crate::mailbox::TicketId;
 use crate::memory::MemorySlug;
 use crate::template::TemplateVersion;
@@ -270,6 +271,85 @@ pub enum DomainEvent {
         /// The project whose index was rebuilt.
         project_id: ProjectId,
     },
+    /// An issue was created.
+    IssueCreated {
+        /// Stable issue id.
+        issue_id: IssueId,
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+    },
+    /// An issue was updated.
+    IssueUpdated {
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// An issue status changed.
+    IssueStatusChanged {
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+        /// New status.
+        status: IssueStatus,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// An issue priority changed.
+    IssuePriorityChanged {
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+        /// New priority.
+        priority: IssuePriority,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// An issue carnet was updated.
+    IssueCarnetUpdated {
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// Two issues were linked.
+    IssueLinked {
+        /// Source issue.
+        issue_ref: IssueRef,
+        /// Target issue.
+        target: IssueRef,
+        /// Link kind.
+        kind: IssueLinkKind,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// Two issues were unlinked.
+    IssueUnlinked {
+        /// Source issue.
+        issue_ref: IssueRef,
+        /// Target issue.
+        target: IssueRef,
+        /// Link kind.
+        kind: IssueLinkKind,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// An agent was assigned to an issue.
+    IssueAgentAssigned {
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+        /// Assigned agent.
+        agent_id: AgentId,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
+    /// An agent was unassigned from an issue.
+    IssueAgentUnassigned {
+        /// Human-friendly issue reference.
+        issue_ref: IssueRef,
+        /// Unassigned agent.
+        agent_id: AgentId,
+        /// New optimistic version.
+        version: IssueVersion,
+    },
     /// A project's memory grew past the recall budget while no embedder is
     /// configured (strategy `none`): the first moment a semantic embedder would
     /// help (ARCHITECTURE §14.5.5, LOT C3). Published **at most once per session per