feat(domain,application,infrastructure,backend,app-tauri,frontend): lot utilisateur #350 — animation d'écartement des onglets au drag/reorder, icônes projet N&B colorisées derrière les messages, tools/skills plugin utilisables par les agents autorisés en headless, refs stables des skills assignés (QA verte)

- Tabs (shared/ui): cible de drop matérialisée par écartement before/after pendant le drag/reorder, reset via rAF sans reliquat, clavier et annonces préservés.
- projectIcons: icônes projet en noir et blanc par défaut, colorisées avec la couleur du projet, occupant la cellule et visibles derrière les messages rendus légèrement transparents.
- Permissions plugin headless: PluginMcpServerSpec transporte l'allowlist exacte authorized_tools regroupée par (pluginId, serverId) depuis les PluginToolRef; projection Codex enabled_tools + default_tools_approval_mode="approve" — une permission déjà accordée au niveau projet/template ne déclenche pas de seconde approbation, un tool non assigné reste hors surface appelable; réserves orchestrator/mcp server+tools alignées, dto backend + dto_agents app-tauri.
- Skills: ref stable plugin:<pluginId>:<skillId> exposée dans le contexte agent, idea_skill_read(ref=...) canonique via read_assigned_by_ref, erreur structurée ambiguousSkillName avec candidates; SkillsPanel dédoublonné (android-build-install); agents-dev/L12-skills.md à jour.
- Docs: ARCHITECTURE.md section 22.3 (projection des autorisations agent vers les runtimes plugin).
- QA verte #350 reconfirmée avant commit.

crates/infrastructure/src/orchestrator/mcp/server.rs

@@ -759,7 +759,17 @@ impl McpServer {
             // (`isError: true`) rather than a protocol error: the agent can read
             // it and decide, and the connection stays healthy.
             Err(e) => {
-                let detail = e.to_string();
+                let detail = match &e {
+                    application::AppError::AmbiguousSkillName { candidates, .. } => {
+                        serde_json::json!({
+                            "code": e.code(),
+                            "message": e.to_string(),
+                            "candidates": candidates,
+                        })
+                        .to_string()
+                    }
+                    _ => e.to_string(),
+                };
                 application::diag!(
                     "[mcp] tools_call end tool={name} requester={requester_label} \
                      target={arg_target} ok=false is_error=true result_len={} elapsed_ms={}",

crates/infrastructure/src/orchestrator/mcp/tools.rs

@@ -521,16 +521,21 @@ pub fn catalogue() -> Vec<ToolDef> {
         },
         ToolDef {
             name: "idea_skill_read",
-            description: "Read the full body of an IdeA skill assigned to you, by name — call this \
+            description: "Read the full body of an IdeA skill assigned to you, preferably by its stable ref. \
+                          Name lookup remains available for compatibility and fails when ambiguous — call this \
                           to actually execute/follow a skill listed in your « Skills disponibles » \
-                          section. Resolves project scope first, then global. Returns the skill's \
+                          section. Returns the skill's \
                           Markdown inline.",
             input_schema: json!({
                 "type": "object",
                 "properties": {
-                    "name": { "type": "string", "description": "Skill name (as listed in your context)." }
+                    "ref": { "type": "string", "description": "Stable skill ref (for example plugin:<pluginId>:<skillId>)." },
+                    "name": { "type": "string", "description": "Legacy skill name lookup (must be unambiguous)." }
                 },
-                "required": ["name"],
+                "anyOf": [
+                    { "required": ["ref"] },
+                    { "required": ["name"] }
+                ],
                 "additionalProperties": false
             }),
         },
@@ -767,6 +772,7 @@ pub fn map_tool_call(
             // The requester (handshake identity) is carried for symmetry with the
             // other read tools; `validate` derives the requester party from it.
             requested_by: Some(requester.to_owned()),
+            skill_ref: s("ref"),
             name: s("name"),
             ..base()
         },
@@ -809,6 +815,7 @@ fn base() -> OrchestratorRequest {
         request_type: None,
         requested_by: None,
         name: None,
+        skill_ref: None,
         target_agent: None,
         profile: None,
         context: None,
@@ -1450,6 +1457,48 @@ mod tests {
         assert!(matches!(err, Err(ToolMapError::Invalid(_))));
     }
 
+    #[test]
+    fn skill_read_prefers_stable_ref_and_keeps_name_compatibility() {
+        let requester = domain::ConversationParty::agent(domain::AgentId::from_uuid(
+            uuid::Uuid::parse_str(REQ).unwrap(),
+        ));
+        assert_eq!(
+            map_tool_call(
+                "idea_skill_read",
+                &json!({ "ref": "plugin:dev.idea.android:build-install" }),
+                REQ,
+            )
+            .unwrap(),
+            OrchestratorCommand::ReadSkill {
+                reference: Some("plugin:dev.idea.android:build-install".to_owned()),
+                name: None,
+                requester: requester.clone(),
+            }
+        );
+        assert_eq!(
+            map_tool_call("idea_skill_read", &json!({ "name": "build" }), REQ).unwrap(),
+            OrchestratorCommand::ReadSkill {
+                reference: None,
+                name: Some("build".to_owned()),
+                requester,
+            }
+        );
+        assert!(matches!(
+            map_tool_call("idea_skill_read", &json!({}), REQ),
+            Err(ToolMapError::Invalid(_))
+        ));
+
+        let tool = catalogue()
+            .into_iter()
+            .find(|tool| tool.name == "idea_skill_read")
+            .unwrap();
+        assert!(tool.input_schema["properties"].get("ref").is_some());
+        assert_eq!(
+            tool.input_schema["anyOf"],
+            json!([{ "required": ["ref"] }, { "required": ["name"] }])
+        );
+    }
+
     #[test]
     fn ask_agent_is_an_inline_reply_tool_but_reply_is_not_exposed() {
         assert!(tool_returns_reply("idea_ask_agent"));

crates/infrastructure/src/plugin/mod.rs

@@ -890,6 +890,7 @@ mod tests {
             env: vec![("PLUGIN_ROOT".to_owned(), "/plugin".to_owned())],
             cwd: "/plugin".to_owned(),
             transport: "stdio".to_owned(),
+            authorized_tools: Vec::new(),
         }
     }