feat(wave): #119/#122/#131/#132 verts + sprint plugins ESM/persistance #135/#136/#139

État d'intégration confiné à la branche batch. Les tickets #119 (skills →
capacités agent découvrables), #122 (override permissions par défaut), #131
(effort par agent/presets) et #132 (outil MCP d'édition du contexte projet)
sont verts en périmètre. Le sprint plugins multi-fichiers ESM / persistance
plugin-owned (#135/#136/#139) est co-implémenté dans les MÊMES fichiers de
câblage (frontend/src/ports/index.ts, backend/src/lib.rs, domain/ports.rs,
backend/dto.rs), inséparable sans staging interactif (indisponible ici).

Commit unique volontaire : préserve l'état vert QA sans découpe hunk risquée.
NON mergé vers develop tant que #137 (QA e2e plugins) n'est pas vert.

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

crates/backend/src/events.rs

@@ -579,6 +579,16 @@ pub enum DomainEventDto {
         #[serde(skip_serializing_if = "Option::is_none")]
         orchestrator: Option<String>,
     },
+    /// The project's global context was written directly.
+    #[serde(rename_all = "camelCase")]
+    ProjectContextUpdated {
+        /// The project whose global context changed.
+        project_id: String,
+        /// Writer party (`"user"` or agent id).
+        by: String,
+        /// Epoch-milliseconds of the write.
+        at_ms: i64,
+    },
     /// A memory note was created or updated.
     #[serde(rename_all = "camelCase")]
     MemorySaved {
@@ -1213,6 +1223,15 @@ impl From<&DomainEvent> for DomainEventDto {
                 project_id: project_id.to_string(),
                 orchestrator: orchestrator.as_ref().map(|a| a.to_string()),
             },
+            DomainEvent::ProjectContextUpdated {
+                project_id,
+                by,
+                at_ms,
+            } => Self::ProjectContextUpdated {
+                project_id: project_id.to_string(),
+                by: conversation_party_wire(*by),
+                at_ms: *at_ms,
+            },
             DomainEvent::MemorySaved { slug } => Self::MemorySaved {
                 slug: slug.as_str().to_string(),
             },
@@ -1426,6 +1445,28 @@ mod tests {
         );
     }
 
+    #[test]
+    fn project_context_updated_relays_writer_to_wire() {
+        let project_id = ProjectId::from_uuid(uuid::Uuid::from_u128(1));
+        let writer = agent(2);
+
+        let dto = DomainEventDto::from(&DomainEvent::ProjectContextUpdated {
+            project_id,
+            by: ConversationParty::agent(writer),
+            at_ms: 987_654,
+        });
+
+        assert_eq!(
+            serde_json::to_value(&dto).unwrap(),
+            json!({
+                "type": "projectContextUpdated",
+                "projectId": project_id.to_string(),
+                "by": writer.to_string(),
+                "atMs": 987654,
+            })
+        );
+    }
+
     #[test]
     fn background_completion_relays_rendezvous_context_to_wire() {
         let project_id = ProjectId::from_uuid(uuid::Uuid::from_u128(1));