feat(source-control): ship the pr_open_state default as ready #8655

Refs: #7576
Refs: #7555
Decision: #7555 (comment) (default); unattended runs: owner 2026-10-20, Decision recorded comment on this issue

Agent Brief

Type: Feature
Summary: The source-control plugin's bundled pr_open_state default flips from draft to ready, so a consumer who sets nothing gets ready PRs. A request for a draft still opens a draft. An unattended run follows pr_open_state the same way an attended run does (owner, 2026-10-20).

Problem: The owner chose open-as-ready (Q501), and #7576 records the setting's default as ready, but the plugin still ships draft. Only repositories that set the key, like this one, get ready PRs.

Current behavior:

• plugins/source-control/.claude-plugin/plugin.json:42-48: pr_open_state "default": "draft", description "draft (default) leaves it for ready to flip later".
• plugins/source-control/README.md:543 repeats "draft" as the default.
• plugins/source-control/skills/pull-request/SKILL.md:50: "with none of them set the state is draft; a repository opts into ready. An unattended run leaves a draft whatever the value."
• plugins/source-control/reference/config-resolution.md:157-176 lists the levels.
• plugins/source-control/skills/pull-request/evals/evals.json cases at lines 330 and 536 expect draft from the default level.
• This repository sets pr_open_state: ready (docs/conventions/source-control.yaml:4).

Desired behavior:

• plugin.json default ready; its description, README.md:543, pull-request/SKILL.md:50 and config-resolution.md say ready is the default and a consumer opts into draft.
• An unattended run follows the resolved pr_open_state like an attended one: drop "An unattended run leaves a draft whatever the value" from pull-request/SKILL.md:50 and every other place the skill says unattended runs always open a draft (search the pull-request skill's files for it), and open as ready when the value resolves ready. The ready flow's holds still apply (ready --unattended and check-ready-holds.sh).
• Unchanged: a request for a draft wins over every level; the repository level is read at the base branch.
• The two default-level eval cases expect ready (create runs the ready phase); the draft-request case still expects draft; an unattended case expects the resolved value.

Key interfaces:

• Setting pr_open_state (bundled default ready).

Done when:

• The diff sets "default": "ready" for pr_open_state in plugins/source-control/.claude-plugin/plugin.json and updates the four texts listed (read from the diff).
• plugins/skill-quality/scripts/check-evals-quality.sh plugins/source-control/skills/pull-request/evals/evals.json exits 0.
• scripts/check-changelog-fragments.sh --check passes, with one major fragment for source-control (a changed default changes behavior for consumers who set nothing).
• CI's check-plugins passes on the PR (a PR check; this run does not run it).
• CI's check-skills passes on the PR (a PR check; this run does not run it).

Out of scope:

• This repository's own value (already ready).
• The other source-control: PR pipeline states, review venue, findings lane and statuses #7576 slices (review venue, findings lane, statuses).

Origin:

• Open every PR as ready: hers (Lauren's opening-a-pr playbook).
• Draft only as a multi-session container: Matt's (implement-spec); kept by the request level.
• Bundled default ready: the owner's (Q501), confirmed 2026-10-20 over the h8 relay that it stays draft.

Do not run with: other pull-request skill changes.

Size Small, Complexity Low, Uncertainty Known.

Slice of #7576 (Phase 8, pr-states), filed from the owner's 2026-10-20 disposition round.