fix: eliminate alt-screen flash when returning from repo/project detail

The hub hands its live terminal to detail/project_detail on open (already
flash-free going in), but both sub-views unconditionally tore the terminal
down on exit; the hub's next loop iteration then always called tui::setup()
again, producing a real LeaveAlternateScreen -> (plain terminal visible for
one frame) -> EnterAlternateScreen blink on every trip back.

- detail::run / project_detail::run now return the live terminal on a clean
  exit instead of tearing it down (only torn down if the inner loop itself
  errors); hub::tui_phase accepts an already-live terminal and skips its own
  setup() when given one, threading it across loop iterations
- project_detail's own nested repo-detail call (Enter on its Repos tab) had
  the same issue one level down, fixed the same way via Option<Tty> so the
  terminal can be taken out for the nested call and put back
- verified via raw pty byte counts: two full hub<->detail round trips now
  show zero EnterAlternateScreen/LeaveAlternateScreen pairs in between,
  vs. one pair per trip before

src/hub/keys.rs

@@ -148,8 +148,16 @@ pub fn maybe_load_activity(state: &mut HubState) {
 /// event, and routes it to whichever input mode is currently active. Modal/
 /// confirm/filter input short-circuit here (they're loop control flow, not
 /// part of the global keymap); everything else goes to `keys_dispatch`.
-pub fn tui_phase(state: &mut HubState) -> Result<(PhaseResult, Option<crate::tui::Tty>)> {
-    let mut terminal = crate::tui::setup()?;
+///
+/// `existing_term` lets the caller hand back a terminal a sub-view (repo/
+/// project detail) just returned instead of tearing down and setting up a
+/// fresh one — the previous "leave alt screen, blink the real terminal,
+/// re-enter" was visible for a frame every time detail handed control back.
+pub fn tui_phase(state: &mut HubState, existing_term: Option<crate::tui::Tty>) -> Result<(PhaseResult, Option<crate::tui::Tty>)> {
+    let mut terminal = match existing_term {
+        Some(t) => t,
+        None    => crate::tui::setup()?,
+    };
     let result = (|| -> Result<PhaseResult> {
         loop {
             state.poll_incoming();

src/hub/mod.rs

@@ -174,8 +174,13 @@ pub async fn run_overview_tui(
         log
     };
 
+    // Carried across loop iterations so a terminal handed back by a sub-view
+    // (repo/project detail) can be reused by the next `tui_phase` call
+    // instead of tearing down and setting a fresh one up — see `tui_phase`'s
+    // doc comment for the flash this avoids.
+    let mut carried_term: Option<crate::tui::Tty> = None;
     loop {
-        let (phase_result, handed_term) = tui_phase(&mut state)?;
+        let (phase_result, handed_term) = tui_phase(&mut state, carried_term.take())?;
 
         if state.quit {
             session::save(state.tab, state.cur_repo_idx().map(|ri| state.repos[ri].path.clone()));
@@ -186,12 +191,14 @@ pub async fn run_overview_tui(
             PhaseResult::OpenDetail => {
                 state.open_detail = false;
                 if let Some(ri) = state.cur_repo_idx() {
-                    let _ = crate::status::detail::run(state.repos[ri].clone(), cfg, handed_term).await;
+                    if let Ok(term) = crate::status::detail::run(state.repos[ri].clone(), cfg, handed_term).await {
+                        carried_term = Some(term);
+                    }
                 } else if let Some(pi) = state.cur_proj_idx() {
                     let repo_indices = state.project_repos(pi);
                     let proj_repos: Vec<RepoSummary> =
                         repo_indices.iter().filter_map(|&ri| state.repos.get(ri)).cloned().collect();
-                    project_detail::run(state.projects[pi].clone(), proj_repos, cfg, handed_term).await?;
+                    carried_term = Some(project_detail::run(state.projects[pi].clone(), proj_repos, cfg, handed_term).await?);
                 }
                 // Detail view can rename/delete/archive repos or change branches —
                 // rescan so the hub's list reflects whatever just happened, instead

src/hub/project_detail.rs

@@ -109,28 +109,41 @@ impl St {
 
 /// Runs the project detail sub-view until the user backs out. Reuses the
 /// caller's terminal handle when given one (avoids an alternate-screen
-/// flash when entering from the hub), otherwise sets up its own.
-pub async fn run(project: Project, repos: Vec<RepoSummary>, cfg: &AppConfig, maybe_term: Option<crate::tui::Tty>) -> Result<()> {
-    let mut terminal = match maybe_term {
+/// flash when entering from the hub), otherwise sets up its own. On a
+/// normal exit, hands the still-live terminal back to the caller instead of
+/// tearing it down, so the hub can reuse it for its own next frame without
+/// the alternate screen toggling off in between; only torn down here if
+/// `run_loop` itself errors.
+pub async fn run(project: Project, repos: Vec<RepoSummary>, cfg: &AppConfig, maybe_term: Option<crate::tui::Tty>) -> Result<crate::tui::Tty> {
+    // `Option` (rather than a bare `Tty`) so the Enter-on-Repos branch below
+    // can `take()` it out for the nested `crate::detail::run` call (which
+    // needs to own the terminal to hand it further down) and put the
+    // (possibly-recreated) terminal back afterwards, without ever tearing
+    // down and setting up a fresh one in between.
+    let mut terminal = Some(match maybe_term {
         Some(t) => t,
         None    => crate::tui::setup()?,
-    };
+    });
     let mut st = St::new(project, repos, cfg.clone());
 
     // Spawn commits aggregation immediately
     spawn_commits(&mut st);
 
-    let result = run_loop(&mut st, &mut terminal).await;
-    crate::tui::teardown(terminal)?;
-    result
+    match run_loop(&mut st, &mut terminal).await {
+        Ok(())  => Ok(terminal.expect("terminal always present after a clean run_loop exit")),
+        Err(e)  => {
+            if let Some(t) = terminal.take() { crate::tui::teardown(t)?; }
+            Err(e)
+        }
+    }
 }
 
-async fn run_loop(st: &mut St, terminal: &mut crate::tui::Tty) -> Result<()> {
+async fn run_loop(st: &mut St, terminal: &mut Option<crate::tui::Tty>) -> Result<()> {
     loop {
         poll_commits(st);
         poll_activity(st);
 
-        terminal.draw(|f| super::project_detail_render::draw(f, st))?;
+        terminal.as_mut().expect("terminal present during run_loop").draw(|f| super::project_detail_render::draw(f, st))?;
 
         let event = crate::tui::next_event(250)?;
         let key = match event { Some(Event::Key(k)) => k, _ => continue };
@@ -182,13 +195,13 @@ async fn run_loop(st: &mut St, terminal: &mut crate::tui::Tty) -> Result<()> {
             continue;
         }
 
-        handle_key(key.code, st).await;
+        handle_key(key.code, st, terminal).await;
         if st.quit { break; }
     }
     Ok(())
 }
 
-async fn handle_key(code: KeyCode, st: &mut St) {
+async fn handle_key(code: KeyCode, st: &mut St, terminal: &mut Option<crate::tui::Tty>) {
     st.status_msg = None;
     match code {
         KeyCode::Char('q') | KeyCode::Esc => { st.quit = true; }
@@ -233,7 +246,16 @@ async fn handle_key(code: KeyCode, st: &mut St) {
         KeyCode::Enter => match st.tab {
             ProjectTab::Repos => {
                 if let Some(r) = st.repos.get(st.repo_cursor).cloned() {
-                    let _ = crate::detail::run(r, &st.cfg, None).await;
+                    // Hand our live terminal down (no flash), then take back
+                    // whatever it returns instead of tearing it down here.
+                    let handed = terminal.take();
+                    match crate::detail::run(r, &st.cfg, handed).await {
+                        Ok(t)  => *terminal = Some(t),
+                        // detail::run already tore its (our) terminal down on
+                        // error — nothing left to draw to, so back out clean
+                        // instead of panicking on the next frame's `.expect`.
+                        Err(_) => st.quit = true,
+                    }
                 }
             }
             ProjectTab::Todos => {