One page rule for both ends; the help overlay shows how to page

improvise-5xbq: resolve::page_rows is now the one home of the page-scroll
rule; the TUI's Move calls it instead of repeating visible_rows * 3 / 4.
A lockstep case pages (PgDn/PgUp, Ctrl-d/Ctrl-u) on a non-square window,
8 rows by 3 columns, and pins the TUI's landing rows as well as comparing
host and client, since one home moves both ends together. Both faults
the ticket injected (page_rows = window_rows / 2; paging by window_cols)
now fail at the first PgDn, before and after the move to one home.

improvise-1c5m: the help overlay draws the mode's own hint (hint_line,
the string #hint carries) in a sticky footer, so a narrow window whose
app bar wraps under #help still says how to page. Playwright case at
600px, red at base, and red again with the footer made non-sticky.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdfEGXA7aJ6ftMsCc9PJze

web/style.css

@@ -736,6 +736,17 @@ td.total {
   font-weight: 700;
 }
 
+/* Sticky, so the paging keys stay in view however long the page scrolls. */
+.help-footer {
+  position: sticky;
+  bottom: -1.25rem;
+  margin: 0.75rem 0 0;
+  padding: 0.5rem 0;
+  border-top: 1px solid var(--line);
+  background: var(--bg);
+  color: var(--dim);
+}
+
 .help-body {
   display: grid;
   grid-template-columns: 16rem 1fr;