fix(state): jangan bangun mention index di mode attach

AppStateRest::new() men-spawn thread ignore::Walk untuk mention_index
tanpa syarat, padahal mode --attach cuma dipakai untuk render lokal —
handle_key dan logika mention berjalan di sisi daemon lewat IPC, jadi
index di client attach tidak pernah dipakai. Ini bikin setiap
--attach melakukan full workspace walk (sampai 50.000 entry) sia-sia.

Pindahkan thread-spawn itu ke method terpisah
spawn_mention_index_build(), dipanggil eksplisit dari
run_single_process() dan run_daemon() setelah AppStateRest::new(),
tapi sengaja tidak dipanggil dari run_attach().

src/app/state/rest.rs

@@ -206,45 +206,54 @@ impl AppStateRest {
             });
         }
 
-        // Fire-and-forget background file index build for `@file` mention
-        // autocomplete.
-        //
-        // Flow: spawn OS thread -> `ignore::Walk` each workspace root,
-        // collecting file paths (workspace-index-prefixed for roots beyond
-        // the first, matching `resolve_path`'s `[N]path` convention) -> stop
-        // once 50,000 entries are collected -> store the result in
-        // `mention_index`.
-        //
-        // Why a raw thread and not a background tokio task: there is no
-        // persistent async runtime driving the render loop, and this is
-        // blocking filesystem I/O -- a dedicated thread keeps startup
-        // non-blocking. Not joined, same rationale as the LSP provisioning
-        // thread above: a slow/huge repo must not delay the TUI appearing.
-        {
-            let mention_index = state.mention_index.clone();
-            let roots = state.workspace_roots.clone();
-            std::thread::spawn(move || {
-                const MAX_MENTION_ENTRIES: usize = 50_000;
-                let mut paths = Vec::new();
-                'roots: for (i, root) in roots.iter().enumerate() {
-                    for entry in ignore::Walk::new(root).flatten() {
-                        if !entry.path().is_file() {
-                            continue;
-                        }
-                        let rel = entry.path().strip_prefix(root).unwrap_or(entry.path());
-                        let rel_str = rel.display().to_string();
-                        let formatted = if i == 0 { rel_str } else { format!("[{i}]{rel_str}") };
-                        paths.push(formatted);
-                        if paths.len() >= MAX_MENTION_ENTRIES {
-                            break 'roots;
-                        }
+        state
+    }
+
+    /// Spawn the background thread that walks every workspace root and
+    /// populates `mention_index` for `@file` mention autocomplete.
+    ///
+    /// Why a separate method, not called from `new()`: the attach-only
+    /// TUI client also constructs an `AppStateRest` (for local rendering
+    /// state) but never runs tools or `handle_key` locally — it forwards
+    /// keystrokes to the daemon over IPC, which has its own `AppStateRest`
+    /// with its own index. Spawning this walk in the attach client would
+    /// waste a full workspace scan for an index nothing there consumes.
+    /// Callers that DO need the index (single-process mode, the daemon)
+    /// call this explicitly after construction.
+    ///
+    /// Flow: spawn OS thread -> `ignore::Walk` each workspace root,
+    /// collecting file paths (workspace-index-prefixed for roots beyond
+    /// the first, matching `resolve_path`'s `[N]path` convention) -> stop
+    /// once 50,000 entries are collected -> store the result in
+    /// `mention_index`.
+    ///
+    /// Why a raw thread and not a background tokio task: there is no
+    /// persistent async runtime driving the render loop, and this is
+    /// blocking filesystem I/O -- a dedicated thread keeps startup
+    /// non-blocking. Not joined, same rationale as the LSP provisioning
+    /// thread above: a slow/huge repo must not delay the TUI appearing.
+    pub fn spawn_mention_index_build(&self) {
+        let mention_index = self.mention_index.clone();
+        let roots = self.workspace_roots.clone();
+        std::thread::spawn(move || {
+            const MAX_MENTION_ENTRIES: usize = 50_000;
+            let mut paths = Vec::new();
+            'roots: for (i, root) in roots.iter().enumerate() {
+                for entry in ignore::Walk::new(root).flatten() {
+                    if !entry.path().is_file() {
+                        continue;
+                    }
+                    let rel = entry.path().strip_prefix(root).unwrap_or(entry.path());
+                    let rel_str = rel.display().to_string();
+                    let formatted = if i == 0 { rel_str } else { format!("[{i}]{rel_str}") };
+                    paths.push(formatted);
+                    if paths.len() >= MAX_MENTION_ENTRIES {
+                        break 'roots;
                     }
                 }
-                mention_index.set(paths);
-            });
-        }
-
-        state
+            }
+            mention_index.set(paths);
+        });
     }
 
     /// Whether an agent turn is currently running.

src/main.rs

@@ -109,6 +109,7 @@ fn run_single_process() -> Result<()> {
         &session_dir,
         store.memory_dir,
     );
+    state.spawn_mention_index_build();
     state.sessions = model::session::Session::list(&store.base_dir);
 
 
@@ -442,6 +443,7 @@ fn run_daemon() -> Result<()> {
         &session_dir,
         store.memory_dir,
     );
+    state.spawn_mention_index_build();
     state.sessions = model::session::Session::list(&store.base_dir);
 
     let _rt = tokio::runtime::Runtime::new()?;