An empty range written back to event acts on the word a click there expands to, as acme's expand does

`ML960 960` or `MX1 1` written back with no text acted on the empty range
between the offsets: a look of nothing, an exec of nothing. A click at a
point expands to the word or file name under it, and acme's written-back
event does the same. It now expands with look.expandedWord, as a no-drag
click does, on its line of the body or tag. fs.md says so.

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

1 files changed, 3 insertions, 2 deletions

diff --git a/docs/fs.md b/docs/fs.md
index 7111de1c..337e31eb 100644
--- a/docs/fs.md
+++ b/docs/fs.md
@@ -571,8 +571,9 @@ text, which may hold newlines.
   its text (`FX0 0 1 6 Msg hi`).
 
 Write a record back to have it done as the click would: `<o><a><q0> <q1>\n`
-acts on that range (the last record of a write needs no newline); the whole record as read acts on its text (the only way
-for `0 0`). A chorded record with its two follow-ups, in one write or
+acts on that range (the last record of a write needs no newline), and an
+empty one (`MX12 12`) on the word or file name a click there expands to;
+the whole record as read acts on its text (the only way for `0 0`). A chorded record with its two follow-ups, in one write or
 three, runs once with its argument. `I`, `D`, `i`, `d` are refused. A helper
 holding `event` that writes its own pane's `exec` gets its command back as a
 record: run it through `ctl` instead.