Just: draw the separator out of the # that starts it

A `#` followed by dashes reads as two things, a comment marker and then a
rule. Repeating the `#` makes it one, and the line is a shell comment for
the same reason it is a rule.

Width is unchanged at 57 columns with no terminal, so logs keep their
shape; only the glyph differs.

The `#` stays in `cmd_sep` rather than moving into the rule, so a preset
`JUST_CMD_RULE` cannot produce a line that the shell would try to run.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: redsun82

misc/just/README.md

@@ -164,6 +164,6 @@ counting measurements. Presetting `JUST_CMD_RULE` skips all of them, and is also
 fix the width in CI or in a recording.
 
 With no terminal to ask — a pipe, a log, a shell without `stty` — it falls back to a
-fixed 56 characters, so anything not attached to a terminal looks as it always did. That
-is one branch rather than a platform test: `just` runs `sh` everywhere, so Windows takes
+fixed 57 columns, so logs and CI output are the same width every time. That is one
+branch rather than a platform test: `just` runs `sh` everywhere, so Windows takes
 whichever arm fits rather than a path of its own.

misc/just/defs.just

@@ -20,8 +20,11 @@ error := f'{{ style("error") }}error{{ NORMAL }}: '
 # the terminal from stdin, so it answers when stdout is piped. The arithmetic is in the
 # shell because just has no integers.
 #
-# With no terminal the value is non-numeric and this falls back to the 56 dashes used
-# before. That is a branch, not a platform test: just runs `sh` everywhere.
+# With no terminal the value is non-numeric and this falls back to a fixed 57 columns.
+# That is a branch, not a platform test: just runs `sh` everywhere.
+#
+# The leading `#` is in `cmd_sep`, not in the rule, so the line stays a comment whatever
+# `JUST_CMD_RULE` is set to.
 #
 # Exported and preferred over measuring: `shell()` runs on every parse, so a forwarded
 # verb would otherwise re-measure in every child it spawns, and `if` is lazy in its
@@ -30,7 +33,7 @@ error := f'{{ style("error") }}error{{ NORMAL }}: '
 _rule := if env('JUST_CMD_RULE', '') != '' { env('JUST_CMD_RULE', '') } else { shell('''
     w=$(stty size 2>/dev/null | cut -d" " -f2)
     case "$w" in '' | *[!0-9]*) w=57 ;; esac
-    printf "%*s" $((w - 1)) "" | tr " " -
+    printf "%*s" $((w - 1)) "" | tr " " '#'
 ''') }
 
 export JUST_CMD_RULE := _rule