docs(contributing): define limits for illustrative drafts before work acceptance #4952

User Story

As an OpenShell maintainer coordinating contributor reviews, I want contributors to be able to show a small proposed approach before their work is accepted, while keeping the review request reasonable for maintainers.

Description

Define and document when a contributor may open a draft PR for unaccepted work to illustrate an approach. This is a separate policy decision from moving unaccepted ready-for-review PRs back to draft.

Decide limits on the size and scope of an illustrative draft, the context it must provide, and the review expectations it creates. A 5,000-line draft is too much to ask maintainers to read speculatively. Do not pick an arbitrary line-count threshold without discussion.

The policy should distinguish a focused illustration from a substantial implementation submitted before acceptance, and explain when discussion or a smaller example is the appropriate next step. A draft should not itself imply that the work is accepted or that maintainers have committed to reviewing or merging it.

Context

Follow-up to review of #4948. Related to #4839.

Current contributor and agent guidance requires acceptance even for drafts. Revisit that guidance together once the boundaries of this exception have been agreed.

Definition of Done

• Agree on the purpose, permitted scope, and size limits of an illustrative draft for unaccepted work.
• Define the context contributors should supply and the review expectations for contributors and maintainers.
• Include examples of a useful small illustration and a draft that is too large or broad.
• Document the agreed rule in one canonical place, with references from relevant contributor and agent guidance.
• Identify and resolve any conflicting automation or contribution instructions without treating a draft as work acceptance.