Give photo its command line back, and cover the parser that lost it

[kyu-softmatter]

python -m photo.cli has raised TypeError on every invocation since G10 was removed — --help included:

TypeError: _ActionsContainer._get_positional_kwargs() missing 1 required positional argument: 'dest'

3695b22 ("Remove G10, and leave its number vacant") deleted the body of the --bleach-photons argument and left the call behind:

    c.add_argument("--lifetime-ns", type=float, default=None)
    c.add_argument(
    )

argparse constructs every argument while building the parser, so an empty call fails there rather than at parse time. That is why nothing worked, not even asking for help. Removing the two lines is the whole fix — the gate itself was never broken.

Why the suite did not catch it

The 1210 tests all passed, and would have kept passing. They call evaluate() and the check functions directly; the parser is only built inside main(), and main() is only reached from a shell. So the defect was invisible to the suite and immediate to anyone who typed the command.

tests/test_cli_parsers.py closes that for all ten */cli.py modules rather than just this one: --help must exit 0. The packages are discovered by glob, so a new lens's CLI is covered the day it lands instead of the day someone remembers the file.

Checked both ways — it fails on photo with the empty call restored, and passes with it removed:

$ git stash -- photo/cli.py && pytest -q tests/test_cli_parsers.py
FAILED tests/test_cli_parsers.py::test_cli_help_exits_cleanly[photo] - TypeError
1 failed, 10 passed

$ git stash pop && pytest -q tests/test_cli_parsers.py
11 passed

Full suite with the fix: 1210 passed, 11 skipped.

How it was found

Trying to run the photo gate on TRITC, to see what supplying a literature fluorescence lifetime would unblock. The entry for that is a separate pull request and it depends on this one — its ## What it supplies section quotes this CLI's before/after output, which a reviewer cannot reproduce until this lands.

🤖 Generated with Claude Code