feat(orchestrator): modèle de désignation d'orchestrateur + sink de diagnostic

Introduit le modèle AgentManifest { version, entries, orchestrator } et la
garde d'écriture directe may_write_directly(..., &OrchestratorDesignation) :
seul l'orchestrateur désigné peut écrire directement, les autres passent par
le rendez-vous médié. Câble la désignation à travers domain → application →
infrastructure → app-tauri (context_guard, service, lifecycle, ports).

Ajoute crates/application/src/diag.rs : sink de diagnostic best-effort, sans
dépendance, qui miroite les traces du rendez-vous inter-agents de
l'orchestrateur vers un fichier de log persistant (utile au lancement via
AppImage où stderr est jeté), avec la même discipline « zéro dépendance,
ne casse jamais le rendez-vous ».

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

crates/domain/src/permission.rs

@@ -894,8 +894,11 @@ pub trait PermissionProjector: Send + Sync {
     ///
     /// `eff == None` ⇒ the **empty** projection ([`PermissionProjection::empty`]):
     /// we keep the CLI's native prompting (the product invariant of [`resolve`]).
-    fn project(&self, eff: Option<&EffectivePermissions>, ctx: &ProjectionContext)
-        -> PermissionProjection;
+    fn project(
+        &self,
+        eff: Option<&EffectivePermissions>,
+        ctx: &ProjectionContext,
+    ) -> PermissionProjection;
 
     /// Run-dir-relative paths of the [`ProjectedFile::Replace`] files this
     /// projector owns, so the swap path can clean them up when an agent moves
@@ -1448,7 +1451,10 @@ mod tests {
         let md = render_permission_summary(Some(&eff)).expect("a posed policy renders a summary");
 
         // Files: OS-enforced / Landlock when supported.
-        assert!(md.contains("OS-enforced"), "files block must say OS-enforced");
+        assert!(
+            md.contains("OS-enforced"),
+            "files block must say OS-enforced"
+        );
         assert!(md.contains("Landlock"), "files block must name Landlock");
         // Commands: advisory, NOT OS-locked, and the why (ExecuteBash).
         assert!(md.contains("advisory"), "commands must be called advisory");
@@ -1462,7 +1468,10 @@ mod tests {
         );
         // The actual rules surface in their respective sections.
         assert!(md.contains("`src/**`"), "the file scope is shown");
-        assert!(md.contains("`rm *` (prefix)"), "the command matcher is shown");
+        assert!(
+            md.contains("`rm *` (prefix)"),
+            "the command matcher is shown"
+        );
         // Resolved posture is surfaced.
         assert!(md.contains("**Default posture:** Ask"));
     }