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

tests/test_milestone_summary_brief.py

@@ -34,6 +34,7 @@ def _milestone(mid: int, status: str, touched_day: int) -> dict:
         "updated_at": "2026-01-01T00:00:00+00:00", "last_touched_at": touched,
         "total": 4, "completed": 2, "pct": 50.0,
         "status_counts": {"todo": 2, "in_progress": 0, "done": 2, "cancelled": 0},
+        "next_step": {"id": 900 + mid, "title": f"M{mid} step 3", "status": "todo"},
     }
 
 
@@ -52,6 +53,10 @@ def test_brief_rows_leave_out_the_plan_and_what_the_caller_already_knows():
         "id": 1, "title": "M1", "description": "what M1 is for", "status": "active",
         "order_index": 1, "total": 4, "completed": 2, "pct": 50.0,
         "status_counts": {"todo": 2, "in_progress": 0, "done": 2, "cancelled": 0},
+        # Trimmed of the plan body, but NOT of which step is next (#4154): the
+        # listing is where "2 of 4 done" gets read, and that number is exactly
+        # what invites a reader to name the open step from memory.
+        "next_step": {"id": 901, "title": "M1 step 3", "status": "todo"},
     }]