Add a label flag to dev.py pr nf-y39l ← Beads

Twinned from https://github.com/cfsh/ninefold/issues/905 by tools/beads/import_github.py's reconcile pass.

See this transcript:

""" open the PR

running Open the PR via dev.py pr Wrote PR body to scratchpad file cat > /tmp/claude-0/-root-nf-devs-argo/bdef4cf1-44cd-4eb4-9ac8-b1d362fa6e2e/scratchpad/pr-body.md <<'EOF' Records the pair-programming arrangement for this worktree in CLAUDE.local.md, per notes/pair-programming.md: pairing agreed, rev:off agreed as Aedan's standard for pairing worktrees, and the branch-off-main-tip note since main is checked out elsewhere.

Aedan, in chat: > we are going to do pair-coding > rev:off for this worktree (and should be the case in pair-programming as > standard) EOF cat /tmp/claude-0/-root-nf-devs-argo/bdef4cf1-44cd-4eb4-9ac8-b1d362fa6e2e/scratchpad/pr-body.md Records the pair-programming arrangement for this worktree in CLAUDE.local.md, per notes/pair-programming.md: pairing agreed, rev:off agreed as Aedan's standard for pairing worktrees, and the branch-off-main-tip note since main is checked out elsewhere.

Aedan, in chat: > we are going to do pair-coding > rev:off for this worktree (and should be the case in pair-programming as > standard) Failed to run Open PR with rev:off label via dev.py pr ./dev.py pr -F /tmp/claude-0/-root-nf-devs-argo/bdef4cf1-44cd-4eb4-9ac8-b1d362fa6e2e/scratchpad/pr-body.md --label rev:off 2>&1 Exit code 2 usage: dev.py [-h] <verb> ... dev.py: error: unrecognized arguments: --label rev:off Checked dev.py pr flags ./dev.py pr --help 2>&1 usage: dev.py pr [-h] --body-file PATH [--title TITLE] [--chunk CHUNK] [--draft] [--base BASE] [--branch BRANCH]

options: -h, --help show this help message and exit --body-file PATH, -F PATH the PR body: Summary + Test Plan. The **Session:** line is added for you if you did not write one --title TITLE, -t TITLE PR title (default: the first commit's subject) --chunk CHUNK chunk name for the Session line, e.g. 'dev.py pr' --draft open as a draft (CLAUDE.md: real PRs over drafts — reserve this for genuinely exploratory work) --base BASE base branch (default: main, or the branch you are on when it already has an open PR) --branch BRANCH name for the new branch when stacking (default: the current branch with the next free -N suffix) Open the PR via dev.py pr running ./dev.py pr -F /tmp/claude-0/-root-nf-devs-argo/bdef4cf1-44cd-4eb4-9ac8-b1d362fa6e2e/scratchpad/pr-body.md 2>&1

"""