fix: keep stepped range progress totals aligned

[GHX5T-SOL]

This pull request was authored by a coding agent.

Summary

• Fix mo.status.progress_bar(range(...)) when total is inferred, so stepped ranges track the number of yielded items instead of advancing past the inferred total.
• Preserve existing explicit-total behavior for stepped ranges, where range.step is used with the caller-provided total.
• Add regressions for both inferred and explicit totals on range(0, 10, 2).

Closes #9575.

Validation

• uv run --group test pytest tests/_plugins/stateless/status/test_progress.py -q (15 passed)
• uv run ruff check marimo/_plugins/stateless/status/_progress.py tests/_plugins/stateless/status/test_progress.py
• uv run ruff format --check marimo/_plugins/stateless/status/_progress.py tests/_plugins/stateless/status/test_progress.py
• uv run --only-group typecheck mypy marimo/_plugins/stateless/status/_progress.py
• git diff --check
• git diff | gitleaks stdin --no-banner --redact --timeout 30

Limitations

• I ran focused Python/status validation only; I did not run the full test suite or a browser UI smoke.
• I did not take any account/legal action for the CLA beyond reading the contribution guidance.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	May 18, 2026 8:01pm

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[cubic-dev-ai]

No issues found across 2 files

Architecture diagram

sequenceDiagram
    participant User as User Code
    participant PB as progress_bar()
    participant PR as ProgressBar <br/>_progress.py
    participant PBar as Progress <br/>bar component
    
    User->>PB: progress_bar(range(0, 10, 2))
    PB->>PR: __init__(collection=range, total=None)
    PR->>PR: total_was_provided = (total is not None)
    PR->>PR: total is None → infer total
    
    alt No explicit total
        PR->>PR: total = len(range) = 5
        PR->>PR: collection is range →<br/>total_was_provided is False →<br/>skip step override
        PR->>PR: step remains default 1
    else Explicit total provided
        User->>PB: progress_bar(range(0, 10, 2), total=10)
        PB->>PR: __init__(collection=range, total=10)
        PR->>PR: total_was_provided = True
        PR->>PR: total = 10 (caller-provided)
        PR->>PR: collection is range AND<br/>total_was_provided is True →<br/>step = collection.step = 2
    end
    
    PR-->>PB: ProgressBar instance
    PB-->>User: ProgressBar instance
    
    Note over User,PBar: Iteration
    
    loop Over range(0, 10, 2)
        User->>PR: next()
        PR->>PBar: update(step=1)
        PBar-->>PR: current += 1
        PR-->>User: [0, 2, 4, 6, 8]
    end
    
    Note over User,PBar: Final state differs by branch
    
    alt No explicit total
        User->>PR: check progress.current, progress.total
        PR-->>User: (5, 5) — tracks yielded items
    else Explicit total
        User->>PR: check progress.current, progress.total
        PR-->>User: (10, 10) — step applied to caller's total
    end

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[mscolnick]

@GHX5T-SOL, please sign the CLA

[GHX5T-SOL]

recheck

[GHX5T-SOL]

I have read the CLA Document and I hereby sign the CLA

[dmadisetti]

Thanks, but this could be an elif

[GHX5T-SOL]

Changed this to an elif in 45db08c. Thanks.