feat: improve terminal navigation and UI behavior

- refine tree and history navigation behavior
- improve scrolling continuity in the terminal UI
- keep AI worklog and prompt log updated
- validate changes with project quality checks

tests/test_ui.py

@@ -10,6 +10,7 @@ from app.ui import (
     TerminalUI,
     build_history_lines,
     build_render_lines,
+    clamp_scroll_offset,
     format_entry,
     move_selection,
     open_terminal_streams,
@@ -79,6 +80,18 @@ def test_build_history_lines_marks_selected_history_entry(tmp_path: Path) -> Non
     ]
 
 
+def test_clamp_scroll_offset_keeps_selection_visible_when_moving_down() -> None:
+    assert clamp_scroll_offset(5, scroll_offset=0, visible_count=3, total_count=10) == 3
+
+
+def test_clamp_scroll_offset_keeps_selection_visible_when_moving_up() -> None:
+    assert clamp_scroll_offset(1, scroll_offset=4, visible_count=3, total_count=10) == 1
+
+
+def test_clamp_scroll_offset_returns_zero_when_all_items_fit() -> None:
+    assert clamp_scroll_offset(2, scroll_offset=1, visible_count=5, total_count=3) == 0
+
+
 def test_toggle_history_mode_selects_current_history_entry(tmp_path: Path) -> None:
     root = tmp_path / "root"
     child = root / "child"
@@ -134,6 +147,80 @@ def test_history_mode_toggle_off_keeps_current_directory(tmp_path: Path) -> None
     assert navigator.current_path == root.resolve()
 
 
+def test_right_arrow_expands_collapsed_directory(tmp_path: Path) -> None:
+    workspace = tmp_path / "workspace"
+    scripts = workspace / "scripts"
+    build = scripts / "build"
+    workspace.mkdir()
+    scripts.mkdir()
+    build.mkdir()
+
+    navigator = Navigator(workspace)
+    navigator.set_selected_index(1)
+    ui = TerminalUI()
+
+    assert ui._handle_tree_key(curses.KEY_RIGHT, navigator) is None
+    assert navigator.current_path == workspace.resolve()
+    assert [entry.name for entry in navigator.visible_entries] == [
+        "..",
+        "scripts",
+        "build",
+    ]
+
+
+def test_right_arrow_enters_already_expanded_directory(tmp_path: Path) -> None:
+    workspace = tmp_path / "workspace"
+    scripts = workspace / "scripts"
+    build = scripts / "build"
+    workspace.mkdir()
+    scripts.mkdir()
+    build.mkdir()
+
+    navigator = Navigator(workspace)
+    navigator.set_selected_index(1)
+    navigator.expand_selected_directory()
+    ui = TerminalUI()
+
+    assert ui._handle_tree_key(curses.KEY_RIGHT, navigator) is None
+    assert navigator.current_path == scripts.resolve()
+    assert navigator.selected_index == 0
+
+
+def test_left_arrow_goes_to_parent_when_selected_entry_is_collapsed(
+    tmp_path: Path,
+) -> None:
+    parent = tmp_path / "parent"
+    current = parent / "current"
+    child = current / "child"
+    parent.mkdir()
+    current.mkdir()
+    child.mkdir()
+
+    navigator = Navigator(current)
+    navigator.set_selected_index(1)
+    ui = TerminalUI()
+
+    assert ui._handle_tree_key(curses.KEY_LEFT, navigator) is None
+    assert navigator.current_path == parent.resolve()
+    assert navigator.selected_index == 0
+
+
+def test_enter_returns_selected_path_without_navigating(tmp_path: Path) -> None:
+    workspace = tmp_path / "workspace"
+    child = workspace / "child"
+    workspace.mkdir()
+    child.mkdir()
+
+    navigator = Navigator(workspace)
+    navigator.set_selected_index(1)
+    ui = TerminalUI()
+
+    result = ui._handle_tree_key(10, navigator)
+
+    assert result == child.resolve()
+    assert navigator.current_path == workspace.resolve()
+
+
 def test_open_terminal_streams_raises_without_terminal(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None: