feat(planning): gate principle and reversibility threads at handoff, plan and plan-reviewer #8335

Parent

Refs #8326 · Source: PLAN Phase 5, topic malleable-design-defaults

Depends on

• feat(planning): design defaults name the principles; add lifecycle and reversibility #8334

Outcome

Plan-time checks enforce the new threads.

• /planning:design-handoff fails unless the principle and reversibility threads are RESOLVED, directional, or TAGGED-DEFERRED. For a prototype they are skipped and named.
• /planning:plan Step 2's design-default checklist checks the same threads and copies the Quality bar: line into the review brief of each tagged phase.
• planning:plan-reviewer's Design alignment axis flags a plan that spreads one fact across files or rebuilds what existing code already does.
• The plan template states when a phase is tagged Review: code-design: any phase that adds or changes a contract, type, module, or a fact or rule that several files read, skill and instruction Markdown included. Only trivial edits omit the tag. The template also maps concurrency to /review:quality-gate slice concurrency.

Key interfaces

From the plan's ## Design:

planning design-handoff, plan Step 2, plan-reviewer | principle and reversibility threads gated; plan-time cascade/reuse gap | proactive check

plan-reviewer Design alignment gains: "Does the planned file list or design place one fact or rule in several files, or build what existing code already does?"

Conventions followed: the plan template's phase Review: tags; the plan-reviewer's review axes.

Done when

• grep -c "one fact or rule in several files" on the plan-reviewer context returns 1.
• Eval cases (case.yaml dirs under the planning plugin's evals/): dh-missing-reversibility-thread-fails, and the outcome case plan-reviewer-flags-spread-fact (a plan whose file list repeats one fact is flagged). /evals:plugin-eval with and without; difference in the PR body.
• After the commit, bash scripts/check-changed-skills.sh origin/main and bash scripts/check-affected.sh --tests exit 0 with no SKIP line.
• A changelog fragment for the planning plugin.

Out of scope

• The dispatch that runs a tagged review (already landed in the implementation plugin).