ui: drop the footer cheatsheet; F1 opens a key reference instead

The permanent Footer spent a screen row on a truncated, always-visible key list.
Remove it (the status line now owns the bottom row) and put the full cheatsheet
behind F1 — grouped by task (Navigate / Views / Move / Edit / Search) rather than
by widget, which is what makes it readable. Esc, F1 or q closes it; there's also
a "Keyboard shortcuts" command-palette entry.

F1 rather than '?' because '?' is already search-backwards in the code views.
Textual leaves F1 unbound (App only claims ctrl+q/ctrl+c), so it traps cleanly.

Gotcha worth recording: the helper that builds the cheatsheet was first called
_render, which collides with Widget._render — Textual invoked ours internally and
got a rich Text where it wanted a Visual, so the whole screen failed to paint
("'Text' object has no attribute 'render_strips'"). Renamed to _cheatsheet.

The search scenario's "rendered above the footer" check now asserts the search
input owns the bottom row instead. New `help` scenario: footer gone, F1 opens it,
groups + real bindings present, Esc closes (5 checks).

Suite note: view_toggle fails in a full run ONLY as collateral from the standing
`filter` flake, which runs immediately before it — when filter leaves the table
empty, view_toggle's open_biggest has nothing to open. Verified: view_toggle
passes alone (13/13) and directly after `help` (18/18), and reproduces as a
cascade with --only filter,view_toggle. Not a regression from this change.

1 files changed, 31 insertions, 7 deletions

diff --git a/tests/test_scenarios.py b/tests/test_scenarios.py
index 1a55f23..c294a9f 100644
--- a/tests/test_scenarios.py
+++ b/tests/test_scenarios.py
@@ -25,11 +25,11 @@ import traceback
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from idatui.app import (  # noqa: E402
     ConfirmScreen, DecompView, DisasmView, FunctionsPanel, HexView, IdaTui,
-    ListingView, StringsPalette, StructEditor, SymbolPalette, XrefsScreen,
-    _str_display, _word_occurrences,
+    HelpScreen, ListingView, StringsPalette, StructEditor, SymbolPalette,
+    XrefsScreen, _str_display, _word_occurrences,
 )
 from textual.widgets import (  # noqa: E402
-    DataTable, Footer, Input, OptionList, Static, TextArea,
+    DataTable, Input, OptionList, Static, TextArea,
 )
 from rich.text import Text  # noqa: E402
 from idatui._sync import wait_for  # noqa: E402
@@ -340,6 +340,30 @@ async def s_command_palette(c: Ctx):
         await c.wait(lambda: app._active != "hex", 5)
 
 
+@scenario("help")
+async def s_help(c: Ctx):
+    app = c.app
+    st = app.query_one("#status", Static)
+    c.check("the status line owns the bottom row (no footer cheatsheet)",
+            st.region.y + st.region.height == app.size.height,
+            f"status={st.region} screen={app.size}")
+    await c.press("f1")
+    opened = await c.wait(lambda: isinstance(app.screen, HelpScreen), 10)
+    c.check("F1 opens the key cheatsheet", opened,
+            f"screen={type(app.screen).__name__}")
+    if not opened:
+        return
+    txt = str(app.screen.query_one("#help-text", Static).render())
+    c.check("it lists the key groups",
+            all(s in txt for s in ("Navigate", "Views", "Move", "Edit", "Search")),
+            txt[:70])
+    c.check("it documents real bindings",
+            "set type" in txt and "split view" in txt and "cross-references" in txt)
+    await c.press("escape")
+    await c.wait(lambda: not isinstance(app.screen, HelpScreen), 10)
+    c.check("Esc closes it", not isinstance(app.screen, HelpScreen))
+
+
 @scenario("strings")
 async def s_strings(c: Ctx):
     app = c.app
@@ -933,10 +957,10 @@ async def s_search(c: Ctx):
     await c.pause(0.1)
     c.check("search bar visible, status hidden (no overlap)",
             si.display and not status.display, f"si={si.display} status={status.display}")
-    footer = app.query_one(Footer)
-    c.check("search input is rendered above the footer (not overlapping)",
-            si.region.height >= 1 and si.region.y < footer.region.y,
-            f"search={si.region} footer={footer.region}")
+    c.check("search input owns the bottom row (nothing overlaps it)",
+            si.region.height >= 1
+            and si.region.y + si.region.height == app.size.height,
+            f"search={si.region} screen={app.size}")
     for ch in term:
         await c.press(ch)
         await c.pause(0.05)