Keep dashes and ellipses with the words they cling to

[gitosaurus]

An em dash written as --- joins two words into a single token, because the
wrapper breaks only on whitespace. That was safe but crude: the pair moved as
a unit and the dash never got a break of its own. Sweeping the cursor across
the margin against a fragment that opens with a dash turned up something
sharper — such a line could run to column 83 in an 80-column terminal.

A fragment starting with punctuation is granted SafetyMargin columns so that
a lone period is not stranded by itself. A hyphen is punctuation, so fifty
characters of prose beginning with a dash collected a concession meant for one
character. The terminal hides this behind the five columns PagedOutput holds
back; --width and the web driver do not.

Three rules, and an ellipsis wants all of them as much as a dash does

• A break may fall on the far side of a run of two or more hyphens or
  periods — the one place inside a word where a line may end. The far side
  must be a word: breaking am I... from ? would strand the question mark,
  which is the fault being repaired rather than a second instance of it.
• No break is chosen that would leave such a run at the head of a line.
  The mark belongs to the word behind it and travels with it.
• The punctuation concession is for a stub of no more than SafetyMargin
  characters, not for any clause that merely opens with a mark.

A single hyphen is left alone. It belongs to the word it joins, and
lead-lined is not a place to break a line.

Where the second rule stops

It governs the break the wrapper chooses. It does not reach the case where
there is no room to choose anything — a fragment opening with a dash arriving
when the line is already full. That one goes down to the next line and starts
it with the mark, which is the same answer the wrapper has always given a word
too long to fit: hold the margin, and let the line begin with whatever had to
be moved.

Honouring the no-leading-dash rule in that case was written first, and it cost
fifteen lines of special handling and a soft margin. Relaxing the rule deleted
the special case and made the margin hard again. Overrunning the margin is the
fault that shows in a narrow window; a line that opens with a dash is not.

Verification

• 18 test suites, 0 failures. Seven new cases in testClingingMarks_ at 20
  columns, covering both sides of a mark, the stranded ?, lead-lined, the
  forced case, and the lone period that the safety margin still rescues.
• Starship and Gorreven produce byte-identical output across the change.
  Neither uses the unspaced forms yet, which is the point: this is inert on
  everything already written, and only changes what happens once --- starts
  appearing in game text.

🤖 Generated with Claude Code

https://claude.ai/code/session_013Ui8UMgev1U8LW5iyQdSsJ