feat(agent): orchestration v3 — surface MCP model-agnostic (M0→M4) — §14.3

Expose l'orchestration IdeA comme serveur MCP par-dessus le même
OrchestratorService::dispatch, avec repli fichier .ideai/requests pour les
CLI sans MCP. v3 réduite à la surface MCP : la messagerie inter-agents et la
corrélation requête↔réponse étaient déjà résolues par §17 (send_blocking).

- M0 capacité MCP sur le profil (McpCapability/McpConfigStrategy/McpTransport)
- M1 injection conf MCP au LaunchAgent + prose adaptée selon la surface
- M2 serveur/adapter MCP (JSON-RPC 2.0 maison ; outils idea_*) + ListAgents
- M3 câblage par projet (registre mcp_servers jumeau du watcher)
- M4 observabilité UI : OrchestratorRequestProcessed.source = file|mcp + badge

Trois portes d'entrée (fichier, MCP, UI) → un seul dispatch ; aucun nouveau
port applicatif ; MCP confiné à l'adapter infra. Tous lots verts (cycle §3).
Cadrage : .ideai/briefs/orchestration-v3-cadrage.md ; ARCHITECTURE.md §14.3.

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

crates/app-tauri/src/events.rs

@@ -12,7 +12,7 @@
 use serde::Serialize;
 use tauri::{AppHandle, Emitter};
 
-use domain::events::DomainEvent;
+use domain::events::{DomainEvent, OrchestrationSource};
 use infrastructure::TokioBroadcastEventBus;
 
 /// Name of the Tauri event carrying relayed [`DomainEvent`]s.
@@ -126,6 +126,10 @@ pub enum DomainEventDto {
         action: String,
         /// Whether IdeA handled it successfully.
         ok: bool,
+        /// Which entry door the request arrived through (`"file"` watcher vs
+        /// `"mcp"` server). Serialised as a lowercase string so the frontend can
+        /// badge the source.
+        source: OrchestrationSourceDto,
     },
     /// A memory note was created or updated.
     #[serde(rename_all = "camelCase")]
@@ -170,6 +174,27 @@ pub enum DomainEventDto {
     },
 }
 
+/// Wire mirror of [`OrchestrationSource`]: which entry door a processed
+/// orchestration request arrived through. Serialised as a lowercase string
+/// (`"file"` / `"mcp"`) the frontend badges on the event.
+#[derive(Debug, Clone, Copy, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub enum OrchestrationSourceDto {
+    /// A `.ideai/requests` JSON file (filesystem watcher).
+    File,
+    /// A `tools/call` on the MCP server.
+    Mcp,
+}
+
+impl From<OrchestrationSource> for OrchestrationSourceDto {
+    fn from(source: OrchestrationSource) -> Self {
+        match source {
+            OrchestrationSource::File => Self::File,
+            OrchestrationSource::Mcp => Self::Mcp,
+        }
+    }
+}
+
 impl From<&DomainEvent> for DomainEventDto {
     fn from(e: &DomainEvent) -> Self {
         match e {
@@ -239,10 +264,12 @@ impl From<&DomainEvent> for DomainEventDto {
                 requester_id,
                 action,
                 ok,
+                source,
             } => Self::OrchestratorRequestProcessed {
                 requester_id: requester_id.clone(),
                 action: action.clone(),
                 ok: *ok,
+                source: (*source).into(),
             },
             DomainEvent::MemorySaved { slug } => Self::MemorySaved {
                 slug: slug.as_str().to_string(),