Reconcile issue status from named delivery slices #2673

Problem

The accepted Base governance design and implementation plan identify package 7c as a required deliverable. This issue translates that package into a reviewed, bounded issue/PR train; it does not authorize implementation before the issue reaches Ready.

Expected behavior

Implement the slice-based issue-status reconciliation described in the accepted design, after readiness and PR-body contracts exist. A slice's state comes from its latest PR; drafts and active implementation remain In Progress; a replaced PR does not make work Done; a closed-unmerged latest PR blocks Done until the maintainer records a disposition. Define completion evidence for planned deliveries with no PR. Apply derivation only after implementation starts and preserve Ready when no PR has begun.

Scope and non-goals

Scope: Implement the slice-based issue-status reconciliation described in the accepted design, after readiness and PR-body contracts exist. A slice's state comes from its latest PR; drafts and active implementation remain In Progress; a replaced PR does not make work Done; a closed-unmerged latest PR blocks Done until the maintainer records a disposition. Define completion evidence for planned deliveries with no PR. Apply derivation only after implementation starts and preserve Ready when no PR has begun.

Non-goals: Do not silently expand scope, activate unreviewed policy, mirror issue fields onto PRs, grant agents merge/release authority, or make changes outside the named affected areas. Any new product decision or materially new work gets a separate issue and decision record.

Affected areas

• issue workflow/checker, Project status derivation and docs/github-workflow.md.
• Accepted source: governance design and implementation plan, PR #2664
• Parent tracker: #2665

Impact and evidence

1. Product intent: Implements only the accepted governance design and plan; any product-requirement change must be filed separately.
2. Architecture and contracts: Destination is the package-specific section of the merged governance design/implementation plan plus the affected canonical contract named above.
3. User guidance: The issue identifies likely guidance paths; the implementation PR must name updated user/FAQ/README paths or give a change-specific reason why none is affected.
4. CLI/API and reference: The affected-area list determines whether CLI/API/reference docs change; the implementation PR must cite the exact reference path or justify no impact.
5. Operations and safety: No privileged automation or merge authority is implied; the PR must list operational/security effects and any rollback.
6. Validation and testing: The issue lists the planned tests; the PR must report executed validation and explain any unavailable test.
7. Examples and downstream use: The implementation PR must identify affected examples/consumers or give evidence that this change has no downstream surface.
8. Governance and contributor process: This package changes or preserves the contributor/governance contract as described in Scope; links must point to the canonical rules.
9. Decision records: No new decision is accepted by this issue; any durable deviation requires a proposed decision record and explicit maintainer acceptance.
10. Release notes: The PR must include a user-facing release-note line or a reasoned none; this issue does not pre-decide that disposition.

These are issue-stage dispositions to refine during Triage. Before Ready, every category must have its exact destination or evidence-based no-impact reason; the PR repeats the ten-category evidence for actual changes.

Open questions

• None known. If implementation exposes an unresolved contract, return this issue to Triage and record the decision before implementation continues.

Plan

• S1: One focused PR for this issue. Use Fixes #N only if no additional slice is needed; if the maintainer approves multiple PRs, name each S1…Sn here before the first is opened and use Part of #N.
• Dependencies: the P2 issue, the P3b issue, the P4 issue, the P6 issue, the P8a issue
• Acceptance criteria:
• Each approved issue slice can be mapped to one or more PRs with an unambiguous latest PR.
• Draft PRs and open implementation work keep the issue In Progress; only all slices in Open-ready or Merged states can make it In Review.
• Done requires every slice merged or closed with a recorded maintainer disposition; one closed-unmerged slice cannot mask unfinished or replacement work.
• No-PR changes have named, reviewable completion evidence; no automation writes status before implementation begins.
• Reconciliation is idempotent, auditable and tested against mixed, replaced, draft, closed-unmerged and no-PR cases.
• Validation:
• Add table-driven state cases covering all transitions and precedence rules.
• Run dry-run against representative live issue/PR histories and compare with maintainer decisions before enabling writes.
• Verify no status write occurs for Ready issues with no PR or before In Progress.
• Risks and rollback: A false Done or In Review status hides work; start read-only/dry-run, retain an explicit maintainer override, and disable reconciliation on mismatch.
• Decision impact: No decision is accepted merely by implementing the issue. Record the relevant accepted decision/ADR and file a superseding record if the maintainer approves a change.