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/io/shell.rs

@@ -1,5 +1,7 @@
+use crate::io::story_metadata::{TestPlanStatus, parse_front_matter};
 use crate::state::SessionState;
 use serde::Serialize;
+use std::fs;
 use std::path::PathBuf;
 use std::process::Command;
 
@@ -8,6 +10,30 @@ fn get_project_root(state: &SessionState) -> Result<PathBuf, String> {
     state.get_project_root()
 }
 
+async fn ensure_test_plan_approved(root: PathBuf) -> Result<(), String> {
+    let approved = tokio::task::spawn_blocking(move || {
+        let story_path = root
+            .join(".story_kit")
+            .join("stories")
+            .join("current")
+            .join("26_establish_tdd_workflow_and_gates.md");
+        let contents = fs::read_to_string(&story_path)
+            .map_err(|e| format!("Failed to read story file for test plan approval: {e}"))?;
+        let metadata = parse_front_matter(&contents)
+            .map_err(|e| format!("Failed to parse story front matter: {e:?}"))?;
+
+        Ok::<bool, String>(matches!(metadata.test_plan, Some(TestPlanStatus::Approved)))
+    })
+    .await
+    .map_err(|e| format!("Task failed: {e}"))??;
+
+    if approved {
+        Ok(())
+    } else {
+        Err("Test plan is not approved for the current story.".to_string())
+    }
+}
+
 #[derive(Serialize, Debug, poem_openapi::Object)]
 pub struct CommandOutput {
     pub stdout: String,
@@ -54,5 +80,30 @@ pub async fn exec_shell(
     state: &SessionState,
 ) -> Result<CommandOutput, String> {
     let root = get_project_root(state)?;
+    ensure_test_plan_approved(root.clone()).await?;
     exec_shell_impl(command, args, root).await
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use tempfile::tempdir;
+
+    #[tokio::test]
+    async fn exec_shell_requires_approved_test_plan() {
+        let dir = tempdir().expect("tempdir");
+        let state = SessionState::default();
+
+        {
+            let mut root = state.project_root.lock().expect("lock project root");
+            *root = Some(dir.path().to_path_buf());
+        }
+
+        let result = exec_shell("ls".to_string(), Vec::new(), &state).await;
+
+        assert!(
+            result.is_err(),
+            "expected shell execution to be blocked when test plan is not approved"
+        );
+    }
+}