feat(plans): milestone-as-plan-container; retire kind=plan (T3)

The milestone becomes the plan container: a new nullable milestones.body
holds the design/intent (Goal/Approach/Verification) and individual steps
live as first-class child tasks (milestone_id) instead of checkboxes crammed
into one kind=plan task body. start_planning now creates a MILESTONE seeded
with the body template (not a kind=plan task) and returns it with applicable
rules; a new get_milestone MCP tool reads the plan back (body + steps + rules).

kind=plan is hard-retired going forward — start_planning never creates one.
The 'plan' task_kind enum value stays valid so the 11 historical plan-tasks
remain readable in place; no body-shredding backfill (corpus review showed
auto-splitting their checklists into tasks would be lossy: embedded code
blocks, a non-binary [~] state, tables, ID-encoded hierarchy).

- migration 0066: add milestones.body
- model/service/route/MCP: body passthrough on create+update; get_milestone
- server _INSTRUCTIONS: "plan" = milestone w/ body + child step-tasks
- UI: ProjectView shows/edits a milestone's plan body; start_planning expands
  the new milestone and opens its plan editor
- tests updated to the milestone contract + new body/get_milestone coverage

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/scribe/mcp/server.py

@@ -17,14 +17,21 @@ Hierarchy: Project -> Milestone -> Task/Note.
 What each part is for, and when to reach for it:
 - Project: the top-level container for a body of work.
 - Milestone: groups related tasks within a project toward a goal (status
-  active/done). Use one when a chunk of work needs its own arc.
+  active/done). A milestone is ALSO the home of a plan — its `body` holds the
+  design/intent (Goal/Approach/Verification) and its child tasks are the steps.
+  Use one when a chunk of work needs its own arc.
 - Task: a unit of actionable work with a lifecycle (status
   todo/in_progress/done/cancelled, optional priority). A task is a note with a
   status — reach for one when there is something to DO. Record progress over
   time with work-logs (add_task_log) rather than rewriting the body.
-- Plan: a task with kind=plan — HOW you'll execute a chunk of work. The body
-  holds the design + step checklist; work-logs record progress. Start one with
-  start_planning when beginning non-trivial work, before you dive in.
+- Plan: a MILESTONE acting as a plan container — HOW you'll execute a chunk of
+  work. The design/intent lives in the milestone `body`; each step is its own
+  child task (create_task(milestone_id=...)), tracked with status + work-logs —
+  NOT a checkbox buried in the body. Start one with start_planning when
+  beginning non-trivial work, before you dive in; read it back with
+  get_milestone (body + steps). (The old kind=plan task is retired — some
+  historical plan-tasks still exist and remain readable, but don't create new
+  ones.)
 - Note: durable free-form knowledge — reference material, decisions, logs of
   what happened.
   No lifecycle, not actionable. Reach for one to CAPTURE something worth keeping.
@@ -147,14 +154,17 @@ adopting or creating — never do either silently, and never guess a project int
 existence. Once a project is in scope, the enter_project handshake and the
 host-memory pointer step above both apply.
 
-Plans are tasks with kind=plan, and Scribe is the canonical home for them.
-When you begin non-trivial work, call start_planning(project_id, title) FIRST —
-before any brainstorming, design, or plan-writing skill runs. start_planning
-seeds the plan body, returns the project's applicable_rules, and gives you the
-task id you'll write into. If a habit tells you to save a plan or spec to a local
-`.md` file, that's superseded here: put the spec/plan content in the kind=plan
-task's body via update_task, and record progress with add_task_log. Local .md
-files are not the record — the task is.
+A plan is a MILESTONE, and Scribe is the canonical home for it. When you begin
+non-trivial work, call start_planning(project_id, title) FIRST — before any
+brainstorming, design, or plan-writing skill runs. start_planning creates the
+milestone, seeds its `body` with the design template, returns the project's
+applicable_rules, and gives you the milestone id you'll write into. Put the
+design/intent in the milestone body via update_milestone(milestone_id, body=...);
+create each step as a child task with create_task(milestone_id=...) and track it
+with status + add_task_log — do NOT list steps as checkboxes in the body. Read
+the plan back with get_milestone (body + steps). If a habit tells you to save a
+plan or spec to a local `.md` file, that's superseded here: the milestone is the
+record, not a local file.
 
 Deletes are recoverable: every delete_* tool moves the entity (and its
 descendants) to the trash and returns a deleted_batch_id. Use list_trash() to
@@ -180,7 +190,7 @@ operator. "Works for one user" is not done.
 # until explicitly classified here.
 _READ_ONLY_TOOLS = frozenset({
     "get_event", "get_note", "get_project", "get_rule", "get_rulebook",
-    "get_task", "get_recent", "enter_project",
+    "get_task", "get_milestone", "get_recent", "enter_project",
     "list_events", "list_lists", "list_milestones", "list_notes",
     "list_persons", "list_places", "list_projects", "list_rulebooks",
     "list_rules", "list_tags", "list_tasks", "list_topics", "list_trash",

src/scribe/mcp/tools/milestones.py

@@ -13,32 +13,75 @@ from __future__ import annotations
 
 from scribe.mcp._context import current_user_id
 from scribe.services import milestones as milestones_svc
+from scribe.services import notes as notes_svc
+from scribe.services import rulebooks as rulebooks_svc
 from scribe.services import trash as trash_svc
 
 
 async def list_milestones(project_id: int) -> dict:
     """List milestones for a Scribe project, ordered by order_index.
 
-    Returns id, title, description, status (active/done), order_index,
-    and task counts.
+    Returns id, title, description, body (the plan/design), status
+    (active/done), order_index, and task counts.
     """
     uid = current_user_id()
     rows = await milestones_svc.get_project_milestone_summary(uid, project_id)
     return {"milestones": rows}
 
 
+async def get_milestone(milestone_id: int) -> dict:
+    """Fetch a milestone (the plan container) with its step-tasks and rules.
+
+    A milestone IS a plan: its `body` holds the design/intent, and its steps
+    are the child tasks listed here. Use this to read a plan top-to-bottom —
+    the body for the design, `steps` for the trackable units of work. Mirrors
+    the planning context that start_planning returns (applicable rules), so the
+    rules surface again on recall.
+
+    Returns: milestone (incl. body), progress, steps (its tasks ordered by
+    status then update), and applicable_rules / subscribed_rulebooks.
+    """
+    uid = current_user_id()
+    milestone = await milestones_svc.get_milestone(uid, milestone_id)
+    if milestone is None:
+        raise ValueError(f"milestone {milestone_id} not found")
+    progress = await milestones_svc.get_milestone_progress(milestone_id)
+    steps, _ = await notes_svc.list_notes(
+        uid, is_task=True, milestone_id=milestone_id, sort="status", limit=200,
+    )
+    applicable = await rulebooks_svc.get_applicable_rules(
+        project_id=milestone.project_id, user_id=uid,
+    )
+    out = milestone.to_dict()
+    out.update(progress)
+    return {
+        "milestone": out,
+        "steps": [t.to_dict() for t in steps],
+        "applicable_rules": applicable["rules"],
+        "subscribed_rulebooks": applicable["subscribed_rulebooks"],
+        "applicable_rules_truncated": applicable["truncated"],
+    }
+
+
 async def create_milestone(
     project_id: int,
     title: str,
     description: str = "",
+    body: str = "",
     status: str = "active",
 ) -> dict:
     """Create a milestone within a Scribe project.
 
+    A milestone can serve as a plan container — put the design/intent in `body`
+    and track each step as a child task (create_task(milestone_id=...)). For a
+    fresh plan, prefer start_planning, which seeds the body template + surfaces
+    the project's rules.
+
     Args:
         project_id: The project this milestone belongs to (required).
         title: Milestone name (required).
-        description: Optional description of what this milestone covers.
+        description: Optional one-line summary of what this milestone covers.
+        body: Optional plan/design (markdown) — the milestone's full plan text.
         status: active (default) or done.
     """
     uid = current_user_id()
@@ -47,6 +90,7 @@ async def create_milestone(
         project_id=project_id,
         title=title,
         description=description or None,
+        body=body or None,
         status=status,
     )
     return milestone.to_dict()
@@ -57,6 +101,7 @@ async def update_milestone(
     milestone_id: int,
     title: str = "",
     description: str = "",
+    body: str = "",
     status: str = "",
     order_index: int = -1,
 ) -> dict:
@@ -67,7 +112,8 @@ async def update_milestone(
             ownership scoping is enforced by user_id at the service layer).
         milestone_id: ID of the milestone to update.
         title: New title, or omit to leave unchanged.
-        description: New description, or omit to leave unchanged.
+        description: New one-line summary, or omit to leave unchanged.
+        body: New plan/design (markdown), or omit to leave unchanged.
         status: New status — active or done.
         order_index: New display position (0-based). Use -1 to leave unchanged.
     """
@@ -77,6 +123,8 @@ async def update_milestone(
         fields["title"] = title
     if description:
         fields["description"] = description
+    if body:
+        fields["body"] = body
     if status:
         fields["status"] = status
     if order_index >= 0:
@@ -101,6 +149,7 @@ async def delete_milestone(milestone_id: int) -> dict:
 def register(mcp) -> None:
     for fn in (
         list_milestones,
+        get_milestone,
         create_milestone,
         update_milestone,
         delete_milestone,

src/scribe/mcp/tools/tasks.py

@@ -233,14 +233,24 @@ async def add_task_log(task_id: int, content: str) -> dict:
 async def start_planning(project_id: int, title: str) -> dict:
     """Begin a plan in Scribe (the preferred home for plans — not a local .md file).
 
-    Creates a plan-task (a task with kind=plan) seeded with a plan template under
-    the given project, and returns it together with the project's applicable
-    Rulebook rules and brief context. Maintain the plan afterwards with the normal
-    task tools (update_task to edit the body, add_task_log to record progress).
+    Creates a MILESTONE that IS the plan: its `body` is seeded with a design
+    template (Goal/Approach/Verification) under the given project, and the call
+    returns it together with the project's applicable Rulebook rules and brief
+    context. The milestone is the plan container — the individual steps live as
+    first-class child tasks under it, not as checkboxes in the body.
+
+    Afterwards:
+    - Edit the plan/design with update_milestone(milestone_id, body=...).
+    - Create each step as its own task with create_task(milestone_id=<this id>);
+      track it with status + add_task_log. Do NOT put steps as checkboxes in the
+      milestone body.
+
+    (kind=plan tasks are retired — use this instead. Existing historical
+    plan-tasks remain readable but new planning goes through milestones.)
 
     Args:
         project_id: The project this plan is for.
-        title: A short title for the plan.
+        title: A short title for the plan/milestone.
     """
     uid = current_user_id()
     return await planning_svc.start_planning(