Story 26: Establish TDD workflow and quality gates

Add workflow engine with acceptance gates, test recording, and review
queue. Frontend displays gate status (blocked/ready), test summaries,
failing badges, and warnings. Proceed action is disabled when gates
are not met. Includes 13 unit tests (Vitest) and 9 E2E tests
(Playwright) covering all five acceptance criteria.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/main.rs

@@ -3,11 +3,13 @@ mod io;
 mod llm;
 mod state;
 mod store;
+mod workflow;
 
 use crate::http::build_routes;
 use crate::http::context::AppContext;
 use crate::state::SessionState;
 use crate::store::JsonFileStore;
+use crate::workflow::WorkflowState;
 use poem::Server;
 use poem::listener::TcpListener;
 use std::path::PathBuf;
@@ -19,10 +21,12 @@ async fn main() -> Result<(), std::io::Error> {
     let store = Arc::new(
         JsonFileStore::from_path(PathBuf::from("store.json")).map_err(std::io::Error::other)?,
     );
+    let workflow = Arc::new(std::sync::Mutex::new(WorkflowState::default()));
 
     let ctx = AppContext {
         state: app_state,
         store,
+        workflow,
     };
 
     let app = build_routes(ctx);