feat: implémentation et QA ticket99 - agent model configuration v2

- backend A-C: VO Codex/Claude, renderers/projecteurs modèle, SecretRef/env, catalogues/use cases/Tauri commands
- frontend D: profils Codex/Claude provider->model->secret, validations, conservation SecretRef
- fix: app-tauri embedded_server isolant IDEA_WEB_ROOT

QA: backend 57/57 tests, frontend 74/74 tests OK

crates/domain/src/permission.rs

@@ -850,6 +850,15 @@ pub struct ProjectionContext<'a> {
     pub project_root: &'a str,
     /// Absolute isolated run dir of the agent (`.ideai/run/<agent-id>/`).
     pub run_dir: &'a str,
+    /// Optional model selected by the agent profile. Orthogonal to permissions:
+    /// projectors may still materialise it even when `eff == None`.
+    pub model: Option<&'a str>,
+    /// Optional Codex `model_provider` value selected by the profile.
+    pub model_provider: Option<&'a str>,
+    /// Optional base URL for a custom Codex model provider.
+    pub model_provider_base_url: Option<&'a str>,
+    /// Optional API-key environment variable name for a model provider.
+    pub model_provider_env_key: Option<&'a str>,
 }
 
 /// One file a projector wants materialised at launch, tagged by **ownership**.