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

plugin/skills/reporting-back/SKILL.md

@@ -66,7 +66,15 @@ it is wrong. So take placement from Scribe:
   the milestone, `position` (step N of M), `progress`, and `next` (the next open
   step). Use those values as they came back.
 - For a wider view, `get_milestone` (a plan and its steps) or `enter_project`
-  (the whole project).
+  (the whole project). Every milestone they list carries **`next_step`** — the
+  earliest step still open, or null when none is — so a reply that says what
+  comes next takes it from the listing it already read. Progress alone says a
+  plan has an open step and not which one, and that is the gap recall fills.
+- **A record you only mention is a record to read.** `placement` rides the
+  write that changed a task, so a task you cite without touching arrives with
+  nothing vouching for it. A retrieval hint carries an id, a kind and a title;
+  where a task stands is in the line's kind marker — `[task (done)]` — and a
+  line you are working from memory has no marker at all.
 - Work with no task behind it: say so plainly — "this wasn't tracked as a
   task" — and offer to record it. An honest "untracked" is a placement too.