feat(placement): a record you only cite carries its status (#4154)

Step 1 made placement cheap for a task whose status CHANGES: create_task
and update_task return where it sits, and the report is written from
that. It did nothing for a task a reply merely cites.

This milestone's own step-6 review reported "#4014 is the open step of
milestone 409". #4014 had been done for four days; the open step was
#4015. The id did not come from a read — it came from a retrieval hint,
which carries an id, a kind and a title and says nothing about status,
while list_milestones said "8 of 9" and would not say which one. The
gap was there to be filled and the nearest-looking id filled it.

Two surfaces, one principle: the status arrives with the id.

1. get_project_milestone_summaries gains next_step — the earliest open
   step, {id, title, status} or None — carried through _BRIEF_FIELDS to
   enter_project, get_project and list_milestones. One extra flat query
   for the whole batch, so #2384's fan-out does not come back.

   OPEN_STEP_STATUSES moves to services/milestones.py and placement.py
   imports it; both surfaces now answer "what is next" and must not
   drift on what counts as open. Both step queries take the same
   readable_notes_clause (rule 78), so a row cannot name a step its own
   progress numbers exclude.

2. _record_kind renders a task's status: [task (done)], [issue (todo)].
   A finished step and an open one read identically before, which is
   exactly the line the misreport was taken from. Only tasks — is_task
   IS status-is-not-None on the model, so there is no fallback branch.

reporting-back gains the practice, owned and registered in the guidance
ownership table: a record you only mention is a record to read.

The guards are structural and each fails on the regression it names:
the query count is asserted rather than the payload shape, and the two
surfaces' agreement is pinned on the rendered ORDER BY, since a mocked
session hands back whatever order the test chose.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

src/scribe/mcp/tools/milestones.py

@@ -24,9 +24,14 @@ async def list_milestones(project_id: int) -> dict:
     """List milestones for a Scribe project, ordered by order_index.
 
     Returns every milestone, done ones included: id, title, description,
-    status (active/done), order_index and progress (total, completed, pct,
-    status_counts). The plan itself is not listed: get_milestone(id) returns a
-    milestone's body and its steps.
+    status (active/done), order_index, progress (total, completed, pct,
+    status_counts) and `next_step`. The plan itself is not listed:
+    get_milestone(id) returns a milestone's body and its steps.
+
+    `next_step` is the earliest step still open — {id, title, status} — or
+    null when the plan has none left. Use it as it came back. "7 of 9 done"
+    invites naming the open one from memory, and a remembered id reads exactly
+    like a read one while being a step that closed days ago.
     """
     uid = current_user_id()
     rows = await milestones_svc.get_project_milestone_summary(uid, project_id)