fix(output): print tab and line-break titles on one line in listings

[ryanlewis]

A task title, tag, project, area or group header that holds a line break used to split its listing row in two. One that holds a tab wrapped onto a second line, because a tab measures as no columns but lipgloss pads it out to four. This is the last step of the internal/output consolidation (#314, #316, #317).

Change

• A new oneLine helper turns each line break into a space: \r\n, \r, \n, vertical tab, form feed, NEL, and the Unicode line and paragraph separators. It does the same for each tab. It runs on the raw text before styling, because lipgloss pads a multi-line styled string to its widest line and expands tabs.
• It applies to task titles, group headers, tags (full and short forms), project rows, area rows, tag rows and their shortcuts, and the candidates listed for an ambiguous task reference.
• I chose a space so the words stay apart, there is still one greppable line per task, and it matches how the agent brief already flattens titles.
• --json, the detail block and the agent brief are unchanged. things show keeps a title's own line breaks, and hang indents them under the value.
• Wide-rune cut: no code change. Half a wide rune can't print, so a cut can stop one cell short, and the column padding fills it. The next column already lines up. A new golden case pins that with two cut CJK rows and their dates.
• Docs.
  • commands.md now says piped output never cuts or shortens a cell, but when any row is wider than 120 columns, whole columns go from every row. It also explains the one-line rule.
  • agents.md said piped output loses its column alignment, which it doesn't. It now says the same as commands.md.
  • SKILL.md gets the one-line rule for agents.

Golden file changes

• 126 of the 130 existing cases are byte-identical.
• The 4 print/tasks-KNOWN-BUG-tab-newline-titles cases (2 widths × 2 colours) are renamed to print/tasks-tab-newline-titles and now show one line per task.
• New cases, each in both colour modes:
  • print/tasks-more-control-chars@40 and @piped: CR and CRLF, a dim title with a newline, a tag with a tab, and a header with a newline.
  • print/collections-control-chars@piped: projects, areas and tags.
  • print/tasks-wide-runes-dated@60 and @40.

Checks

• I built things from main (fcf2779) and from this branch and compared them on an unedited copy of a Things backup, which has no control characters, with HOME pointed at a temporary directory. 19 commands, including show --agent, ran piped and in a pseudo-terminal at 40, 62, 80, 100, 120 and 200 columns, with colour off and on. All 266 pairs were byte-identical. A run of main against itself also gave 0 differences.
• On an edited copy of the backup holding tab, LF, CRLF and CR titles:
  • The today view prints one line per task, piped and on 60- and 40-column pseudo-terminals: 29 task lines for 29 JSON tasks.
  • --json keeps the raw titles.
  • Two cut CJK titles put due: in the same column at 60. At 40 and 50 the date column is dropped, as before.
• New tests: TestOneLine, and TestResolveTaskAmbiguousTitleOnOneLine in cmd.
• make test and make lint pass.

Not changed

• When piped, one very wide row still drops the tags and dates from every row. Joining a multi-line title can make a row wide enough for that. That's the existing drop policy, and the docs now describe it.
• A trailing line break becomes a trailing space.