huskies: merge 1219 story Add runtime artifacts to the default project scaffold .gitignore

server/src/io/fs/scaffold/helpers.rs

@@ -64,6 +64,8 @@ pub(super) fn write_story_kit_gitignore(root: &Path) -> Result<(), String> {
         "store.json",
         "pipeline.db",
         "*.db",
+        "merge_reports/",
+        "session_store.json",
     ];
 
     let gitignore_path = root.join(".huskies").join(".gitignore");

server/src/io/fs/scaffold/mod.rs

@@ -20,6 +20,16 @@ use templates::{
     STORY_KIT_STACK,
 };
 
+/// Retrofit the Story Kit `.gitignore` entries onto a project that was
+/// scaffolded before those entries existed (e.g. `merge_reports/` or
+/// `session_store.json` added in a later release). Idempotent — only
+/// appends lines that are missing, so it is safe to call on every project
+/// open regardless of how old the project's `.huskies/` directory is.
+pub(crate) fn ensure_gitignore_entries(root: &Path) -> Result<(), String> {
+    write_story_kit_gitignore(root)?;
+    append_root_gitignore_entries(root)
+}
+
 pub(crate) fn scaffold_story_kit(root: &Path, port: u16) -> Result<(), String> {
     let story_kit_root = root.join(".huskies");
     let specs_root = story_kit_root.join("specs");

server/src/io/fs/scaffold/tests.rs

@@ -334,6 +334,31 @@ fn scaffold_creates_story_kit_gitignore_with_relative_entries() {
     // Database files must be ignored so novice users don't accidentally commit them
     assert!(sk_content.contains("pipeline.db"));
     assert!(sk_content.contains("*.db"));
+    // Runtime artifacts written under .huskies/ must be ignored too (story 1219)
+    assert!(sk_content.contains("merge_reports/"));
+    assert!(sk_content.contains("session_store.json"));
+}
+
+#[test]
+fn ensure_gitignore_entries_retrofits_already_adopted_project() {
+    // Simulate a project scaffolded before merge_reports/ and session_store.json
+    // were added to the ignore list: .huskies/.gitignore exists but lacks them.
+    let dir = tempdir().unwrap();
+    fs::create_dir_all(dir.path().join(".huskies")).unwrap();
+    fs::write(
+        dir.path().join(".huskies/.gitignore"),
+        "worktrees/\ncoverage/\n",
+    )
+    .unwrap();
+
+    ensure_gitignore_entries(dir.path()).unwrap();
+
+    let sk_content = fs::read_to_string(dir.path().join(".huskies/.gitignore")).unwrap();
+    assert!(sk_content.contains("merge_reports/"));
+    assert!(sk_content.contains("session_store.json"));
+    // Pre-existing entries must survive untouched
+    assert!(sk_content.contains("worktrees/"));
+    assert!(sk_content.contains("coverage/"));
 }
 
 #[test]