An addr, dot or limit pair out of order or past the text is refused as the address form is, not clamped

`#5,#2` and `#2,#99` were refused (addresses out of order, address out of
range), but the pair form `5 2` became 5..5 and `2 99` became 2..end,
silently a different range from the one asked for. A pair is now checked
the same way: past the text is out of range, and an end before its start
is out of order. fs.md says so.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 3 insertions, 1 deletions

diff --git a/docs/fs.md b/docs/fs.md
index 337e31eb..0ec88876 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -447,7 +447,9 @@ warns once.
 
 `addr`, `dot` and `limit` read the pair of byte offsets they take, so
 copying one onto another (`cp $p/addr $p/dot`) is acme's `dot=addr`. A
-write is a pair or an address expression. `addr` names where `data` reads
+write is a pair or an address expression; a pair is checked as an address
+is, `addresses out of order` (`5 2`) or `address out of range` (past the
+text), never clamped. `addr` names where `data` reads
 (to the end of text) and the range `xdata` reads; `dot` is the selection
 (moving it scrolls the pane there); `limit` bounds the end of a forward
 search and reads empty until set. Truncating `dot` empties it, truncating