Advertise the rule screens in the key help

The bottom help still described 4 as "rules" from before the rules list
existed, and never mentioned 5 at all, so the new screen was unreachable
unless you already knew about it.

The transactions line had also outgrown the window: at 137 characters it ran
past the edge of a normal terminal and "q quit" was simply gone. Help now
wraps to the window width instead of being cut off, and that line is shorter.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/money/main.go

@@ -27,7 +27,7 @@ const usage = `money - statement-driven personal finance tracker
 usage: money [--root DIR] <command> [flags]
 
 commands:
-  tui                  browse and tag transactions (default)
+  tui                  browse and tag transactions, build and prune rules (default)
   import               extract transactions from every statement into the index
   retag                re-apply rules.toml to everything already imported
   ls                   list transactions