feat: implement history mode and AI development logging

- add dedicated history mode UI (toggle with `h`)
- allow navigation inside history with arrows
- allow selecting history entries with Enter
- add tests for history mode behavior
- introduce AI development logs (`ai-worklog.md`, `ai-prompts.md`)
- add AI worklog policy to `instructions-agent.md`

tests/test_ui.py

@@ -1,10 +1,14 @@
+import curses
 from pathlib import Path
 
 import pytest
 
 from app.navigator import Navigator, VisibleEntry
 from app.ui import (
+    HistoryLine,
     RenderLine,
+    TerminalUI,
+    build_history_lines,
     build_render_lines,
     format_entry,
     move_selection,
@@ -65,6 +69,71 @@ def test_build_render_lines_marks_selected_entry(tmp_path: Path) -> None:
     ]
 
 
+def test_build_history_lines_marks_selected_history_entry(tmp_path: Path) -> None:
+    first = tmp_path / "first"
+    second = tmp_path / "second"
+
+    assert build_history_lines((first, second), selected_index=1) == [
+        HistoryLine(text=str(first), is_selected=False),
+        HistoryLine(text=str(second), is_selected=True),
+    ]
+
+
+def test_toggle_history_mode_selects_current_history_entry(tmp_path: Path) -> None:
+    root = tmp_path / "root"
+    child = root / "child"
+    root.mkdir()
+    child.mkdir()
+
+    navigator = Navigator(root)
+    navigator.set_selected_index(1)
+    navigator.enter_selected_directory()
+    ui = TerminalUI()
+
+    ui._toggle_history_mode(navigator)
+
+    assert ui._history_mode is True
+    assert ui._history_selected_index == 1
+
+
+def test_history_mode_enter_selects_entry_and_exits(tmp_path: Path) -> None:
+    root = tmp_path / "root"
+    first = root / "first"
+    second = root / "second"
+    root.mkdir()
+    first.mkdir()
+    second.mkdir()
+
+    navigator = Navigator(root)
+    navigator.set_selected_index(1)
+    navigator.enter_selected_directory()
+    navigator.go_to_parent_directory()
+    navigator.set_selected_index(2)
+    navigator.enter_selected_directory()
+
+    ui = TerminalUI()
+    ui._toggle_history_mode(navigator)
+    ui._handle_history_key(curses.KEY_UP, navigator)
+    ui._handle_history_key(10, navigator)
+
+    assert ui._history_mode is False
+    assert navigator.current_path == root.resolve()
+    assert navigator.selected_index == 0
+
+
+def test_history_mode_toggle_off_keeps_current_directory(tmp_path: Path) -> None:
+    root = tmp_path / "root"
+    root.mkdir()
+    navigator = Navigator(root)
+    ui = TerminalUI()
+
+    ui._toggle_history_mode(navigator)
+    ui._toggle_history_mode(navigator)
+
+    assert ui._history_mode is False
+    assert navigator.current_path == root.resolve()
+
+
 def test_open_terminal_streams_raises_without_terminal(
     monkeypatch: pytest.MonkeyPatch,
 ) -> None: