feat(mcp): enter_project names active milestones with no steps as open work (#4076)

A plan written as a milestone with a description and no steps was invisible to
the session handshake: it lists the 5 most recently touched milestones (#4045),
and touching is a step changing, so a step-less milestone can never qualify.
FabledLibrarian's roadmap (nine such milestones) sat unseen while later plans
were opened as new milestones beside the ones that already described them.

enter_project adds `unplanned_milestones`: active milestones with no steps, in
roadmap order, id/title/description, up to 10 with an omitted count, none
repeated from the recent list, and absent when there are none. The docstring
says what they are for: check them before starting a new milestone, and add
steps to a match with create_records(milestone_id=...).

Milestone 415 step 1.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

src/scribe/mcp/tools/projects.py

@@ -48,6 +48,7 @@ async def list_projects() -> dict:
 # characters, past what a client accepts as a tool result (#4045).
 _HANDSHAKE_MILESTONES = 5
 _HANDSHAKE_OPEN_TASKS = 10
+_HANDSHAKE_UNPLANNED = 10
 
 
 async def enter_project(project_id: int) -> dict:
@@ -67,7 +68,8 @@ async def enter_project(project_id: int) -> dict:
 
     Returns a dict with keys: project, milestone_summary, open_tasks, systems,
     design_system, project_rules, pattern_coverage —
-    plus milestone_summary_omitted, inception and systems_bootstrap, each
+    plus unplanned_milestones, milestone_summary_omitted,
+    unplanned_milestones_omitted, inception and systems_bootstrap, each
     present only when it applies (see below).
 
     `project` is id, title, status and the full goal. get_project has the
@@ -79,6 +81,15 @@ async def enter_project(project_id: int) -> dict:
     get_milestone(id) reads a plan and its steps. `milestone_summary_omitted`
     says how many others exist; list_milestones lists them all.
 
+    `unplanned_milestones` is the active milestones that have NO steps yet,
+    in roadmap order (up to 10; `unplanned_milestones_omitted` counts the
+    rest) — id, title and description. They are open work: a plan somebody
+    wrote down and nobody has broken into steps. A milestone with no steps is
+    never touched, so the recent list above can never show one. Before
+    starting a new milestone for work, check whether one of these already
+    describes it; if so, add steps to it with create_records(milestone_id=…)
+    rather than opening a second plan for the same thing.
+
     `open_tasks` is the 10 most recently touched todo / in-progress tasks,
     with or without a milestone. A work-log counts as touching its task. Each
     names its milestone. list_tasks has the rest.
@@ -156,6 +167,11 @@ async def enter_project(project_id: int) -> dict:
         milestone_rows, limit=_HANDSHAKE_MILESTONES,
     )
     milestone_titles = {m["id"]: m.get("title") for m in milestone_rows}
+    unplanned, unplanned_omitted = milestones_svc.unplanned_milestones(
+        milestone_rows,
+        exclude_ids={m["id"] for m in milestone_summary},
+        limit=_HANDSHAKE_UNPLANNED,
+    )
     open_tasks, _ = await notes_svc.list_notes(
         uid, is_task=True, project_id=project_id,
         status=["todo", "in_progress"], sort="touched", limit=_HANDSHAKE_OPEN_TASKS,
@@ -256,6 +272,13 @@ async def enter_project(project_id: int) -> dict:
             f"{omitted} other milestone(s) not listed. "
             f"list_milestones({project_id}) lists every milestone."
         )
+    if unplanned:
+        out["unplanned_milestones"] = unplanned
+    if unplanned_omitted:
+        out["unplanned_milestones_omitted"] = (
+            f"{unplanned_omitted} more active milestone(s) with no steps. "
+            f"list_milestones({project_id}) lists every milestone."
+        )
     if systems_bootstrap:
         out["systems_bootstrap"] = systems_bootstrap
     if inception_ask: