feat(agents): pont Codex inter-agents + readiness/heartbeat lot 1

Deux chantiers livrés au vert (workspace entier : domain+application+
infrastructure 42 + app-tauri --lib 128, 0 échec).

## Codex inter-agents
- domaine: McpConfigStrategy::TomlConfigHome { target, home_env } +
  toml_config_home(...); AgentProfile::materializes_idea_bridge()
  (whitelist Claude/ConfigFile + Codex/TomlConfigHome); McpServerWiring
  + encodeur TOML.
- application: lifecycle apply_mcp_config bras TomlConfigHome (écrit
  {runDir}/<target>, pousse (home_env, parent) dans spec.env);
  guard_mcp_bridge_supported ré-exprimée via materializes_idea_bridge();
  catalogue Codex porte toml_config_home(".codex/config.toml","CODEX_HOME").
- app-tauri: is_codex_mcp_profile, migrate_codex_run_dir,
  mcp_server_entry_toml.
- tests: matrice domaine TomlConfigHome + round-trip dual Claude/Codex
  sur loopback réel (fakes, zéro token).

## Readiness/heartbeat lot 1
- domaine: readiness.rs — ReadinessPolicy::classify (Final => TurnEnded),
  variantes ReplyEvent::Heartbeat / ToolActivity.
- application: drain_with_readiness consulte la policy et appelle
  mark_idle sur le signal déterministe; branché dans ask_agent.
  Corrige la cause racine: une cible qui ne renvoie qu'un Final (sans
  idea_reply) débloque désormais sa file Busy.
- infrastructure: adapters de session émettent Heartbeat/ToolActivity.
- tests: drain_with_readiness_lot1 (points QA 5 & 6) verts.

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

crates/application/src/agent/catalogue.rs

@@ -80,8 +80,11 @@ pub fn reference_profiles() -> Vec<AgentProfile> {
         .expect("codex reference profile is valid")
         .with_structured_adapter(StructuredAdapter::Codex)
         .with_mcp(McpCapability::new(
-            McpConfigStrategy::config_file(".mcp.json")
-                .expect(".mcp.json is a valid relative MCP config target"),
+            // Codex lit ses serveurs MCP dans `$CODEX_HOME/config.toml`, pas `.mcp.json` :
+            // IdeA écrit ce TOML DANS le run dir et pointe `CODEX_HOME` dessus pour
+            // isoler l'agent du `~/.codex` global (miroir du `.mcp.json` de Claude).
+            McpConfigStrategy::toml_config_home(".codex/config.toml", "CODEX_HOME")
+                .expect(".codex/config.toml + CODEX_HOME is a valid MCP config target"),
             McpTransport::Stdio,
         )),
         AgentProfile::new(
@@ -157,18 +160,36 @@ mod mcp_tests {
     }
 
     #[test]
-    fn claude_and_codex_mcp_use_config_file_mcp_json() {
-        for slug in ["claude", "codex"] {
-            let mcp = profile(slug).mcp.expect("mcp present");
-            assert_eq!(
-                mcp.config,
-                McpConfigStrategy::ConfigFile {
-                    target: ".mcp.json".to_owned()
-                },
-                "profile `{slug}` should declare `.mcp.json`"
-            );
-            assert_eq!(mcp.transport, McpTransport::Stdio);
-        }
+    fn claude_mcp_uses_config_file_mcp_json() {
+        let mcp = profile("claude").mcp.expect("mcp present");
+        assert_eq!(
+            mcp.config,
+            McpConfigStrategy::ConfigFile {
+                target: ".mcp.json".to_owned()
+            },
+            "Claude should declare `.mcp.json`"
+        );
+        assert_eq!(mcp.transport, McpTransport::Stdio);
+    }
+
+    #[test]
+    fn codex_mcp_uses_toml_config_home_codex() {
+        // Codex lit `$CODEX_HOME/config.toml`, pas `.mcp.json` : le seed doit déclarer
+        // la stratégie TOML isolée par `CODEX_HOME` (pendant Codex de Claude).
+        let mcp = profile("codex").mcp.expect("mcp present");
+        assert_eq!(
+            mcp.config,
+            McpConfigStrategy::TomlConfigHome {
+                target: ".codex/config.toml".to_owned(),
+                home_env: "CODEX_HOME".to_owned(),
+            },
+            "Codex should declare `.codex/config.toml` + CODEX_HOME"
+        );
+        assert_eq!(mcp.transport, McpTransport::Stdio);
+        assert!(
+            profile("codex").materializes_idea_bridge(),
+            "the Codex seed must materialise the idea bridge"
+        );
     }
 
     #[test]