command_line/: 14 prompt_toolkit menus each reimplement alt-screen lifecycle, pagination keybindings, and split-panel scaffolding — extract a shared menu framework

Summary

The interactive menu family in command_line/ has no shared framework. Each menu independently reimplements the same five pieces of plumbing, and jscpd + manual review confirm the copies have already drifted (inconsistent keybindings, inconsistent pagination math, two different run-loop styles). This is the root cause behind several of the exact clones below and a major contributor to the 600-line-cap violations already filed as #409.

The menu family (all hand-rolling the same scaffolding)

Conservatively ~1,500-2,000 lines of repeated scaffolding across the family.

What every menu duplicates

1. Alt-screen lifecycle — 13 files contain the identical sequence:

   set_awaiting_user_input(True)
   sys.stdout.write("\033[?1049h")
   sys.stdout.write("\033[2J\033[H")
   sys.stdout.flush()
   await asyncio.sleep(0.05)
   try: ...
   finally:
       sys.stdout.write("\033[?1049l")
       sys.stdout.flush()
       set_awaiting_user_input(False)
   

   (rg -c "1049h" command_line/ → 14 hits across 13 files.)

2. Pagination keybindings on mutable-cell state — selected_idx[0] / current_page[0] up/down/left/right handlers calling ensure_visible_page(...). Exact clones found by jscpd:

   • agent_menu.py:576-595 ↔ autosave_menu.py:604-623 (up/down handlers)
   • agent_menu.py:629-652 ↔ autosave_menu.py:671-694 (enter/c-c + Application + alt-screen entry)

3. Application(layout=..., key_bindings=kb, full_screen=False, mouse_support=False) — 14 occurrences, plus the pending_action[0] = ...; event.app.exit() → outer while True dispatch loop pattern (agent_menu 629-700, judges_menu 749-790, uc_menu 798+).

4. Paginated list rendering with manual page math that bypasses the existing pagination.py:

   • mcp/install_menu.py:142-145 and :204-207: total_pages = (len(items) + PAGE_SIZE - 1) // PAGE_SIZE — pagination.get_total_pages() exists for exactly this.
   • jscpd internal clone mcp/install_menu.py:166-183 ↔ :224-241 — the category-list and server-list render loops are the same "prefix + icon + selected-style + page footer" pipeline with renamed variables.

5. Navigation-hint footers — _render_navigation_hints exists twice as near-identical methods: add_model_menu.py:474-499 ↔ mcp/install_menu.py:243-258 (jscpd: add_model_menu.py:466-480 ↔ install_menu.py:233-247); agent_menu/autosave_menu/judges_menu inline the same hint-tuple sequences.

Divergence evidence (the copies are already inconsistent)

• autosave_menu.py:575-576 binds c-p/c-n as Emacs-style aliases for up/down; agent_menu.py:562/574 does not — same UI, different keys.
• judges_menu.py:739-742 binds both escape and c-c to close; agent_menu.py only binds c-c (Esc does nothing in the agent picker).
• mcp/install_menu.py:650 uses time.sleep(0.05) + app.run(in_thread=True) (sync); the rest use await asyncio.sleep(0.05) + await app.run_async().
• install_menu/add_model_menu use class attributes for state; the others use 1-element list cells — two idioms for the same job ("one obvious way" violation).

Proposed abstraction: command_line/menu_framework.py

@asynccontextmanager
async def alt_screen_session():
    """Owns set_awaiting_user_input + alternate-buffer enter/clear/exit."""
    ...

@dataclass
class PaginatedListState:
    items: Sequence
    page_size: int
    selected: int = 0
    page: int = 0
    # move_up/move_down/page_prev/page_next built on pagination.py
    # current_item property; refresh(items, keep_name=...) for post-action reloads

def bind_list_navigation(kb: KeyBindings, state: PaginatedListState,
                         on_change: Callable, *, emacs_aliases=True): ...

def render_hints(lines: list, hints: list[tuple[str, str]]): ...

class SplitPanelMenu:
    """menu Frame + preview Frame in VSplit; subclasses provide
    render_menu(state), render_preview(item), and an actions dict
    {key: callable} replacing the pending_action[0] dance. run() owns
    the Application, alt_screen_session, and the action-dispatch loop."""

Migrating agent_menu + autosave_menu alone would delete ~300 duplicated lines and make Esc/Emacs-alias behavior consistent for free; the full family is a ~1.5k-line reduction and directly helps the #409 size-cap work.

Related (do not duplicate): #409 (file size cap), #429 (restore_autosave_interactively reimplements this yet again), #433 (keymap cancel/pause duplication).

Filed by Zen Reviewer B (code-puppy-60635a) — DRY review round

Start by reading the duplicated scaffolding in command_line/agent_menu.py and command_line/autosave_menu.py, then inspect command_line/pagination.py and the other listed menus. Define the shared pieces in the proposed command_line/menu_framework.py and verify that the migrated menu family uses common lifecycle, navigation, pagination, and dispatch behavior without the repeated scaffolding.