feat(backend): MCP d'édition de templates (#81)

Ajoute le MCP dédié à l'édition de templates : catalogue et classification
des templates (mcp/templates.rs infrastructure + app-tauri), use cases et
provider (application/template), enforcement de la policy des tools (mod.rs,
server.rs, tools.rs), avec la parité côté chemin OpenAI-compatible
(openai_tools.rs x2).

Lots B1 (catalogue/classification), B2 (use cases/provider) et B3
(enforcement policy) livrés en un seul commit cohérent.

QA vert (seul l'échec de bind loopback #80, connu et non-régression, écarté).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

crates/application/src/lib.rs

@@ -164,9 +164,9 @@ pub use template::{
     AgentDrift, CreateAgentFromTemplate, CreateAgentFromTemplateInput,
     CreateAgentFromTemplateOutput, CreateTemplate, CreateTemplateInput, CreateTemplateOutput,
     DeleteTemplate, DeleteTemplateInput, DetectAgentDrift, DetectAgentDriftInput,
-    DetectAgentDriftOutput, ListTemplates, ListTemplatesOutput, SyncAgentWithTemplate,
-    SyncAgentWithTemplateInput, SyncAgentWithTemplateOutput, UpdateTemplate, UpdateTemplateInput,
-    UpdateTemplateOutput,
+    DetectAgentDriftOutput, ListTemplates, ListTemplatesOutput, ReadTemplate, ReadTemplateInput,
+    ReadTemplateOutput, SyncAgentWithTemplate, SyncAgentWithTemplateInput,
+    SyncAgentWithTemplateOutput, UpdateTemplate, UpdateTemplateInput, UpdateTemplateOutput,
 };
 pub use terminal::{
     CloseTerminal, CloseTerminalInput, CloseTerminalOutput, LiveAgentRegistry, LiveSessionKind,

crates/application/src/template/mod.rs

@@ -11,7 +11,7 @@ pub use usecases::{
     AgentDrift, CreateAgentFromTemplate, CreateAgentFromTemplateInput,
     CreateAgentFromTemplateOutput, CreateTemplate, CreateTemplateInput, CreateTemplateOutput,
     DeleteTemplate, DeleteTemplateInput, DetectAgentDrift, DetectAgentDriftInput,
-    DetectAgentDriftOutput, ListTemplates, ListTemplatesOutput, SyncAgentWithTemplate,
-    SyncAgentWithTemplateInput, SyncAgentWithTemplateOutput, UpdateTemplate, UpdateTemplateInput,
-    UpdateTemplateOutput,
+    DetectAgentDriftOutput, ListTemplates, ListTemplatesOutput, ReadTemplate, ReadTemplateInput,
+    ReadTemplateOutput, SyncAgentWithTemplate, SyncAgentWithTemplateInput,
+    SyncAgentWithTemplateOutput, UpdateTemplate, UpdateTemplateInput, UpdateTemplateOutput,
 };

crates/application/src/template/usecases.rs

@@ -134,9 +134,47 @@ impl UpdateTemplate {
 }
 
 // ---------------------------------------------------------------------------
-// ListTemplates / DeleteTemplate
+// ReadTemplate / ListTemplates / DeleteTemplate
 // ---------------------------------------------------------------------------
 
+/// Input for [`ReadTemplate::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ReadTemplateInput {
+    /// Template to read.
+    pub template_id: TemplateId,
+}
+
+/// Output of [`ReadTemplate::execute`].
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ReadTemplateOutput {
+    /// The requested template.
+    pub template: AgentTemplate,
+}
+
+/// Reads one template from the global store.
+pub struct ReadTemplate {
+    templates: Arc<dyn TemplateStore>,
+}
+
+impl ReadTemplate {
+    /// Builds the use case.
+    #[must_use]
+    pub fn new(templates: Arc<dyn TemplateStore>) -> Self {
+        Self { templates }
+    }
+
+    /// Reads one template.
+    ///
+    /// # Errors
+    /// - [`AppError::NotFound`] if the template is unknown,
+    /// - [`AppError::Store`] on persistence failure.
+    pub async fn execute(&self, input: ReadTemplateInput) -> Result<ReadTemplateOutput, AppError> {
+        Ok(ReadTemplateOutput {
+            template: self.templates.get(input.template_id).await?,
+        })
+    }
+}
+
 /// Output of [`ListTemplates::execute`].
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ListTemplatesOutput {

crates/application/tests/template_usecases.rs

@@ -18,8 +18,8 @@ use uuid::Uuid;
 
 use application::{
     CreateAgentFromTemplate, CreateAgentFromTemplateInput, CreateTemplate, CreateTemplateInput,
-    DetectAgentDrift, DetectAgentDriftInput, SyncAgentWithTemplate, SyncAgentWithTemplateInput,
-    UpdateTemplate, UpdateTemplateInput,
+    DetectAgentDrift, DetectAgentDriftInput, ReadTemplate, ReadTemplateInput,
+    SyncAgentWithTemplate, SyncAgentWithTemplateInput, UpdateTemplate, UpdateTemplateInput,
 };
 
 // ---------------------------------------------------------------------------
@@ -224,6 +224,29 @@ async fn create_template_starts_at_initial_version() {
     assert_eq!(store.list().await.unwrap().len(), 1);
 }
 
+#[tokio::test]
+async fn read_template_returns_one_template_or_not_found() {
+    let existing = template(tid(7), "Base", "body", 3);
+    let store = FakeTemplates::with(vec![existing.clone()]);
+    let read = ReadTemplate::new(Arc::new(store));
+
+    let out = read
+        .execute(ReadTemplateInput {
+            template_id: existing.id,
+        })
+        .await
+        .unwrap();
+    assert_eq!(out.template, existing);
+
+    let err = read
+        .execute(ReadTemplateInput {
+            template_id: tid(8),
+        })
+        .await
+        .expect_err("unknown template should be not found");
+    assert_eq!(err.code(), "NOT_FOUND");
+}
+
 #[tokio::test]
 async fn update_template_bumps_version_and_publishes_event() {
     let store = FakeTemplates::with(vec![template(tid(1), "T", "v1", 1)]);