feat: guide contributions from initial work through review and submission #147

Summary

Please offer a guided contribution workflow that helps users track and resume work from choosing a task through preparing it for review and submitting it.

Problem or workflow

Enthusiasts and small teams often contribute to several projects with different rules. It is easy to lose track of the intended scope, completed checks, unfinished work, or whether a contribution has actually been submitted.

Affected area

Project contribution, Git workflows, review preparation, and publication.

Proposed behavior

Bring the existing contribution-related guidance together into a clear progress view for each task. Help users follow the receiving project's rules, keep unrelated work separate, preserve useful checkpoints, and resume with a clear next step after interruption. Distinguish work in progress, ready for review, ready for submission, and confirmed submission. Let users prepare everything for review before deciding to publish.

For example, someone returning to a contribution after a week should be able to see its purpose, completed work, remaining checks, and submission status without reconstructing the history.

This request concerns the contribution journey; repository settings and presentation are a separate concern covered by #109.