Answer --help so agents can open files in Omawrite

[jankeesvw]

Ask a coding agent to open a Markdown file in Omawrite and the first thing it does is check how the command works. That check never comes back.

What an agent does

Four agents, same instruction ("open <file> in Omawrite"), no other guidance. Three of the four reached for --help before anything else. Taken from ps, not from what they reported:

22:10:29  omawrite --help
22:10:29  omawrite --help
22:10:30  omawrite --help
22:10:45  omawrite .../d.md      (15s later)
22:11:22  omawrite .../b.md      (52s later)
22:11:26  omawrite .../e.md      (56s later)
22:11:37  omawrite .../c.md      (67s later)

None of them got an answer:

$ omawrite --help 2>&1; echo "EXIT:$?"
EXIT:0

Omawrite has no --help (or prints nothing to stdout/stderr).

So they went looking elsewhere. Between them, before any of them opened the file, they ran:

$ cat /usr/bin/omawrite | head -50          # 44KB of ELF
$ strings /usr/bin/omawrite | grep -iE "usage|open|error|help"
$ find / -iname "*omawrite*" ...            # whole filesystem, 3-5s
$ cat /usr/share/applications/omawrite.desktop

They all got there in the end, 15 to 67 seconds later, by guessing that a bare file argument would work. Each --help also put a window on screen showing Could not open --help. in the footer.

Why

main.cpp passes argv[1] straight to Backend::open() as a file name, so --help is read as a file that cannot exist. Nothing reaches the terminal, and the process stays up until the window is closed.

Built from master (8f98892) on Arch with Qt 6.11.2, run with QT_QPA_PLATFORM=offscreen:

$ omawrite --help
(no output, killed after 15s, never exits on its own)

$ omawrite -h
(no output, killed after 15s, never exits on its own)

$ omawrite --nope
(no output, killed after 15s, never exits on its own)

After

Same machine, same Qt, this branch:

$ omawrite --help
Omawrite is a dead-simple Markdown writing app.

Usage:
  omawrite [FILE]

Opens the Omawrite window. FILE is the Markdown file to open; without
one, Omawrite starts on an empty document, or on the draft recovered
from the last session.

Options:
  -h, --help    Show this message and exit

Omawrite is a graphical app: it needs a desktop session, and it keeps
running until the window is closed. Scripts and agents that only want
a file on screen should background it:

  omawrite draft.md &

Everything else is a keyboard shortcut. Ctrl+? lists them in the app,
and https://github.com/omacom-io/omawrite#shortcuts has the same list.

(exit 0, 17ms)

$ omawrite --nope
omawrite: unrecognized option '--nope'

(usage follows on stderr, exit 1, 16ms)

omawrite FILE is unchanged: it opens the window and stays up as before.

What changed

Arguments are parsed in a small src/cli.cpp before QApplication is constructed, so the usage prints even without a desktop session to open a window in. Anything starting with a dash that isn't -h/--help gets an error plus the usage on stderr and exit 1, instead of being treated as a file name.

There's a test in tests/tst_omawrite.cpp; bin/test passes 13/13.

I left --version out because there is no version constant in the source yet. Happy to add one if you want it.