Clarify that completed tasks do not imply archive readiness #1790

Summary

When all tracked tasks are checked, openspec instructions apply currently reports:

All tasks are complete! This change is ready to be archived.

Tracked task completion is narrower than the decision to archive. A project may require additional review or verification, while another user may archive immediately.

A related task-authoring problem surfaced in the BGEE world map editor: its custom policy requires every tracked task to be complete before archive, but its task lists have included archive and later delivery steps. Stock OpenSpec warns about incomplete tasks and permits proceeding after confirmation or with --yes. The hard deadlock comes from the stricter project policy.

Example

- [x] Implement and verify the change
- [ ] Archive the change
- [ ] Verify the archived result

The final two entries cannot be completed before archive. They therefore remain incomplete when stock OpenSpec checks progress, and create a circular dependency when a project requires zero incomplete tasks before archive. Simply omitting those steps can lose useful follow-up information.

Proposed behavior

• Report that all tracked tasks are complete, leaving the archive decision to the project's workflow.
• In the built-in spec-driven guidance, track implementation and verification work that can finish before archive.
• When the requested workflow includes archive or work requiring this change to be archived, preserve those steps as plain bullets in an optional ## Workflow follow-up section at the end of tasks.md. The bullets are reference information outside tracked task progress.
• Allow review and verification before archive regardless of whether they run locally or through hosted services. The guidance should work with GitHub, other tools, or no version control.

Completion wording:

All tracked tasks are complete. Review or verify the change as appropriate before archiving.

Optional follow-up example:

## Workflow follow-up

- Archive the change after the project's review requirements are satisfied.
- Verify the archived result.

Acceptance criteria

• state: "all_done" and existing progress fields remain unchanged.
• Task parsing, validation, archive behavior, and command flags remain unchanged.
• Task-authoring guidance identifies where follow-up information belongs, with a plain-bullet example that does not affect task counts.
• Apply skill and command variants use the same completion semantics.
• Regression tests cover the output, progress compatibility, and generated-template parity.

This is an advisory improvement intended to help avoid circular generated task lists. Projects remain responsible for enforcing their archive policy and deciding how review evidence remains valid across later commits.

Related context

• Proposal: Support human-only tasks in tasks.md (AI skips work it can't do) #1362 discusses routing work at authoring time instead of expanding checkbox state semantics.
• Proposal: prepare → agent work → validate → confirm → finalize flow for archive #1460 proposes a broader archive execution redesign; this smaller guidance correction can stand independently.

AI assistance disclosure

Original research and drafting used OpenAI Codex with gpt-5.6-sol at xhigh reasoning effort. Subsequent review and revisions used OpenAI Codex with GPT-6 Astra.