feat(server): sous-commande idea --serve avec serveur HTTP sécurisé pairing+cookie (#13)

Lot B3 du chantier server/client mode : socle serveur sécurisé exposant le
cœur backend en mode client/serveur, sans PTY (reporté B5).

- crates/app-tauri/src/server.rs : sous-commande --serve, serveur HTTP
  sécurisé — /api/invoke sur allowlist, /api/pair → cookie de session,
  Origin strict, refus du secret en query, gate de bind. 16 tests dont les
  2 refus de sécurité (pairing_rejects_wrong_code,
  invoke_rejects_invalid_session_cookie).
- crates/app-tauri/src/lib.rs : câblage de la sous-commande --serve.
- crates/app-tauri/src/commands.rs : adaptations.
- crates/app-tauri/Cargo.toml : deps bytes/cookie/http/http-body-util,
  feature tokio net. Cargo.lock synchronisé.

Validé : cargo check --workspace vert, app-tauri 267 tests verts, cœur
backend agnostique confirmé, desktop non régressé.

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

crates/app-tauri/src/commands.rs

@@ -113,6 +113,17 @@ pub async fn create_project(
 pub async fn open_project(
     project_id: String,
     state: State<'_, AppState>,
+) -> Result<ProjectDto, ErrorDto> {
+    open_project_for_adapter(project_id, &state).await
+}
+
+/// Shared `open_project` adapter body used by desktop IPC and the HTTP server.
+///
+/// Keeps the non-presentation side effects attached to project opening in one
+/// place while B3 adds a second driving adapter.
+pub(crate) async fn open_project_for_adapter(
+    project_id: String,
+    state: &AppState,
 ) -> Result<ProjectDto, ErrorDto> {
     let id = parse_project_id(&project_id)?;
     let output = state

crates/app-tauri/src/lib.rs

@@ -21,6 +21,7 @@ pub mod mcp_bridge;
 pub mod mcp_endpoint;
 pub mod openai_tools;
 pub mod pty;
+pub mod server;
 pub mod state;
 pub mod stream;
 pub mod tickets;
@@ -42,14 +43,17 @@ use state::AppState;
 /// The `argv[1]` subcommand token that switches the binary into the headless
 /// `mcp-server` **bridge** mode (cadrage v5 §1.3) instead of launching Tauri.
 pub const MCP_SERVER_SUBCOMMAND: &str = "mcp-server";
+/// The `argv[1]` subcommand token that starts the secure HTTP server adapter.
+pub const SERVE_SUBCOMMAND: &str = "--serve";
 
 /// Process entry point: routes `argv` **before** anything Tauri/WebKit is touched.
 ///
 /// When invoked as `<exe> mcp-server …` (an MCP CLI spawned us from the injected
 /// `.mcp.json` declaration), we run the **stdio↔loopback bridge** headless and
-/// **never** initialise the webview — see [`mcp_bridge::run_mcp_bridge`]. Any other
-/// invocation is the normal IDE launch: [`run`] (which blocks until the window
-/// closes and then exits the process itself).
+/// **never** initialise the webview — see [`mcp_bridge::run_mcp_bridge`]. When
+/// invoked as `<exe> --serve …`, we run the secure HTTP adapter headless. Any
+/// other invocation is the normal IDE launch: [`run`] (which blocks until the
+/// window closes and then exits the process itself).
 ///
 /// Returns the [`ExitCode`] for the bridge path; the normal path does not return.
 #[must_use]
@@ -61,6 +65,11 @@ pub fn dispatch() -> ExitCode {
         let rest: Vec<String> = args.map(|a| a.to_string_lossy().into_owned()).collect();
         return mcp_bridge::run_mcp_bridge(rest);
     }
+    let mut args = std::env::args_os().skip(1);
+    if args.next().is_some_and(|a| a == *SERVE_SUBCOMMAND) {
+        let rest: Vec<String> = args.map(|a| a.to_string_lossy().into_owned()).collect();
+        return server::run_from_args(rest);
+    }
 
     run();
     ExitCode::SUCCESS