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/domain/src/events.rs

@@ -5,6 +5,21 @@ use crate::ids::{AgentId, ProfileId, ProjectId, SessionId, SkillId, TemplateId};
 use crate::memory::MemorySlug;
 use crate::template::TemplateVersion;
 
+/// Which entry door a processed orchestration request arrived through.
+///
+/// IdeA exposes the *same* [`crate::OrchestratorService::dispatch`] behind two
+/// substitutable driving adapters (ARCHITECTURE §14.3 + cadrage `orchestration-v3`):
+/// the `.ideai/requests` filesystem watcher and the MCP server. This tag — set by
+/// the adapter that received the request, never inferred in the application — lets
+/// the presentation layer surface *how* a delegation came in.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum OrchestrationSource {
+    /// A JSON request file dropped under `.ideai/requests/`.
+    File,
+    /// A `tools/call` on the MCP server.
+    Mcp,
+}
+
 /// Events emitted by the domain/application as state changes occur.
 ///
 /// Deliberately *not* `Serialize`/`Deserialize`: events are an in-process
@@ -109,6 +124,9 @@ pub enum DomainEvent {
         action: String,
         /// Whether IdeA handled it successfully.
         ok: bool,
+        /// Which entry door the request arrived through (file watcher vs MCP),
+        /// tagged by the receiving adapter.
+        source: OrchestrationSource,
     },
     /// A memory note was created or updated (`.md` written, index upserted).
     MemorySaved {