quest: a quest's PR leaves its quest accurate

quest/m0/README.md

@@ -36,6 +36,7 @@ ownership-manifest design:
 ## Required
 
 - [Finished milestone links](/quest/m0/milestone-links.md) - `quest check` flags a Required link to a milestone with no Required left, so its dependents get unblocked
+- [Accurate landed quests](/quest/m0/landed-quests.md) - a quest-branch PR deletes or rewrites its quest, and `quest check --base` refuses one that does neither
 - [Expensive command gate](/quest/m0/local-gate.md) - shared CPU admission across worktrees and repositories
 - [Recoverable worktrees](/quest/m0/worktree.md) - disk admission, checkpoints, release, and restore
 - [Agent lifecycle integration](/quest/m0/worktree-agents.md) - reclaim completed and suspended checkouts through their harness

quest/m0/landed-quests.md

@@ -0,0 +1,78 @@
+# [S] A quest's PR leaves its quest accurate
+
+## Goal
+
+A PR merged from a quest's branch leaves the tree accurate: a PR that
+finishes its quest deletes the file and every link to it, and a PR that
+leaves work rewrites the quest to that remainder instead of noting it only
+in the PR body. Merging refuses a quest-branch PR that does neither.
+
+In moq-dev/moq on 2026-10-20, the `audit-quests` run found quests left
+behind by merged PRs from their own branches. Three finished their quest
+without deleting it ([moq-dev/moq#5926](https://github.com/moq-dev/moq/pull/5926),
+[#5992](https://github.com/moq-dev/moq/pull/5992),
+[#5993](https://github.com/moq-dev/moq/pull/5993)). Three partial drafts
+merged through `/quest-complete` with the remainder written only in the PR
+body ([#5989](https://github.com/moq-dev/moq/pull/5989),
+[#5991](https://github.com/moq-dev/moq/pull/5991),
+[#6006](https://github.com/moq-dev/moq/pull/6006)). Stale quests then rank as
+ready work and get picked up again. No skill step deletes or trims the quest,
+and `merge` enables auto-merge without looking at the file.
+
+Non-goals: judging whether a rewrite is a faithful remainder (the agent and
+reviewers still do), and PRs not on a quest branch, such as a contributor's
+fork branch that implements a quest; those skip the guard. Merges that
+bypass the merge skill, such as a maintainer's click on GitHub or in the
+[decision inbox](/quest/m0/kix/merge.md), are guarded only where the
+repository runs the guard as a required check; the hosted service has no
+checkout to diff.
+
+## Plan
+
+Decided 2026-10-20 (user, planned from moq-dev/moq):
+
+- One quest: the guide rule and the mechanical guard land together.
+- State the rule once, in `assets/AGENTS.md`'s Execution section next to the
+  existing "When a quest is complete" paragraph: the PR that finishes a quest
+  deletes its file and every link to it, and a PR that leaves work rewrites
+  the quest to what remains. The other skills already read the guide, so they
+  don't repeat it. Update `README.md`'s matching sentence if it disagrees.
+  Rejected: repeating the rule in start, iterate, ready, merge, and complete.
+- Guard: `quest check --base <ref>`. When the head branch is a quest branch
+  (`quest/<path>`, the quest's path without `.md`), the diff from the merge
+  base of `<ref>` must delete or modify that quest file (`quest/<path>.md`, or
+  `quest/<path>/README.md` for an epic); otherwise it is a finding naming the
+  quest and the rule. A head branch that is not a quest branch, or names no
+  existing quest at the base, adds no finding. The head defaults to the
+  current branch; `--branch <name>` overrides it, because agents often push a
+  differently named local branch to the quest branch with an explicit
+  refspec. A plain `quest check` is unchanged. The diff needs git, not a
+  forge, so it lives in `src/cli/` beside the other git callers and keeps
+  `src/core` free of it. Rejected: a CI action alone (skills would run
+  nothing locally), and a skill step alone with no code.
+- A modified file passes even if the edit does not trim the quest (a link
+  fix, say). Accepted: the guard is a floor against forgetting, not a review.
+- `assets/skills/merge.md` fetches the PR's base and head, then runs
+  `quest check --base <remote>/<base> --branch <head>` on a checkout of the
+  PR head before enabling auto-merge. A stale or missing local base branch
+  would put the merge base before the quest existed and skip it. On a
+  finding, it fixes the branch: delete the quest and its links, or rewrite it
+  to the remainder the PR body names, then push, re-check, and continue. It
+  asks the user only when what remains is unclear. `/quest-complete` and
+  `/quest-ready` reach merging through the merge skill, so they need no change
+  of their own. Rejected: refusing and reporting for `/quest-iterate`.
+- Repositories may also run the guard in CI on pull requests; document the
+  invocation in `README.md`, but don't ship a workflow.
+- [Move and delete quests](/quest/m0/helpers/move.md) gives `quest rm`, which
+  the fix-up step uses once it lands; until then the agent deletes and
+  unlinks by hand.
+
+Tests: a quest-branch diff that deletes the quest, one that edits it, and one
+that leaves it untouched (the finding); an epic branch checked against its
+README; a non-quest branch; a branch naming a quest that does not exist at
+the base; and `--branch` overriding the current branch.
+
+## Related
+
+- [Move and delete quests](/quest/m0/helpers/move.md) - `quest rm` deletes a quest and every link to it
+- [Finished milestone links](/quest/m0/milestone-links.md) - the same "a finishing PR removes what depended on it" rule for milestones