feat: finalise ticket99 - implémentation agent model configuration v2

- agent/lifecycle.rs: lifecycle management per profile
- agent/provider_catalogue.rs: provider registration with model support
- agent/usecases.rs: usecases for profile-based agent invocation
- agent/mod.rs: expose agent capabilities via AgentManager
- backend/dto.rs: AgentModelConfig, AgentProviderConfig DTOs
- domain/profile.rs: extend Profile avec agent capabilities
- domain/permission.rs: permission checks pour agent access
- infrastructure/assistant/mod.rs: agent integration
- infrastructure/permission/{claude,codex}.rs: permission handlers
- web-server/lib.rs: agent endpoints
- commands.rs: agent commands
- frontend/adapters/{http,profile,mock,domain}.ts: adapters
- frontend/first-run/FirstRunWizard.{test.tsx,tsx}: first-run flow

crates/infrastructure/src/assistant/mod.rs

@@ -235,6 +235,7 @@ impl TicketAssistantEnvironmentPreparer {
                     &declaration,
                     cwd.as_str(),
                     project.root.as_str(),
+                    profile.model.as_deref(),
                 );
                 self.write_file(&path, rendered.as_bytes()).await?;
                 env.push((home_env.clone(), parent_dir(cwd, target)));
@@ -511,12 +512,13 @@ fn codex_config_toml(
     mcp_declaration: &str,
     run_dir: &str,
     project_root: &str,
+    model: Option<&str>,
 ) -> String {
-    let mut text = replace_toml_table_block(
-        existing.unwrap_or_default(),
-        "mcp_servers.idea",
-        mcp_declaration.trim_end(),
-    );
+    let mut text = existing.unwrap_or_default().to_owned();
+    if let Some(model) = model {
+        text = set_top_level_toml_value(&text, "model", model);
+    }
+    text = replace_toml_table_block(&text, "mcp_servers.idea", mcp_declaration.trim_end());
     text = ensure_codex_project_trust(&text, run_dir);
     text = ensure_codex_project_trust(&text, project_root);
     if !text.ends_with('\n') {
@@ -525,6 +527,33 @@ fn codex_config_toml(
     text
 }
 
+fn set_top_level_toml_value(input: &str, key: &str, value: &str) -> String {
+    let line = format!("{key} = {}", toml_quoted(value));
+    set_top_level_toml_line(input, key, &line)
+}
+
+fn set_top_level_toml_line(input: &str, key: &str, replacement: &str) -> String {
+    let needle = format!("{key} =");
+    let mut out = Vec::new();
+    let mut replaced = false;
+    for line in input.lines() {
+        let trimmed = line.trim_start();
+        if !replaced && trimmed.starts_with(&needle) {
+            out.push(replacement.to_owned());
+            replaced = true;
+        } else {
+            out.push(line.to_owned());
+        }
+    }
+    if !replaced {
+        if !out.is_empty() && !out.first().is_some_and(|line| line.trim().starts_with('[')) {
+            out.push(String::new());
+        }
+        out.insert(0, replacement.to_owned());
+    }
+    out.join("\n")
+}
+
 fn replace_toml_table_block(existing: &str, table: &str, replacement: &str) -> String {
     let header = format!("[{table}]");
     let mut out = Vec::new();