perf: stream the listing incrementally instead of load_all on open (M4)

Opening a listing walked the WHOLE segment (load_all) before showing anything --
a blank pane for seconds on a big .text. Now _prime loads just the viewport
around the cursor (appears instantly) and _grow streams the rest in the
background, growing virtual_size as pages land (throttled). Search finishes
loading first (needs the whole segment).

ListingModel gains a _load_lock so the grower and an in-view search can both
drive page loads without double-fetching; new public load_next_page.

Verified: ensure(1100)->partial(1500,incomplete), load_all->full(5036,complete);
3 concurrent loaders -> 0 duplicate heads; UI listing+search 30/0 (in-process).

1 files changed, 11 insertions, 0 deletions

diff --git a/idatui/domain.py b/idatui/domain.py
index f26354c..e70182c 100644
--- a/idatui/domain.py
+++ b/idatui/domain.py
@@ -526,8 +526,19 @@ class ListingModel:
         self._next: int | None = seg_start  # next address to fetch from
         self._done = False
         self._lock = threading.Lock()
+        # Serializes page loads so a background grower and an in-view search can
+        # both drive loading without double-fetching the same page.
+        self._load_lock = threading.Lock()
+
+    def load_next_page(self) -> int:
+        """Load one more page of heads; returns how many were added."""
+        return self._load_next_page()
 
     def _load_next_page(self) -> int:
+        with self._load_lock:
+            return self._load_next_page_locked()
+
+    def _load_next_page_locked(self) -> int:
         with self._lock:
             if self._done or self._next is None:
                 return 0