feat: show keybindings in a normal-mode popup

src/main.rs

@@ -30,6 +30,7 @@ Use sslmode=disable only for trusted local connections.
 The inspector needs 70×17 terminal cells; PostgreSQL/SQLite windows need 74×22/74×18.
 
 Navigation:
+  ?             Show keybindings in Normal mode (Esc/Enter/? closes)
   Tab/Shift-Tab Cycle explorer, query editor, and rows/schema
   Up/Down, j/k  Move selection; Enter connects/expands a database or opens a relation
   Home/End, g/G First / last item
@@ -41,7 +42,8 @@ Navigation:
   r             Refresh relations and the active relation
   Connected databases have a trailing * and show their tables/views beneath them.
   Enter on the connected database collapses/expands it without reconnecting.
-  Navigation help has its own bordered pane and wraps when needed.
+  Keybindings float above the workspace; Up/Down/jk scroll, Home/End/g/G jump.
+  Query Insert mode and connection/password fields keep ? as literal text.
   Full-width bars show dbdash/provider/READ ONLY above and mode/database below.
   Only badges have colored backgrounds; the remaining bar area uses terminal defaults.
   Focused inputs show one-based line:column (Unicode characters, not screen cells).