feat(inception): the doors — create_project/decide_project_inception take the decision, enter_project asks until decided, REST inception endpoints, _INSTRUCTIONS (#2882, milestone 297 step 4)

- MCP create_project(..., exclude_always_on_rulebooks, subscribe_rulebooks,
  design_system_id (0 unstated / -1 none / n), seed_systems): any inception
  arg → inception.decide(via="mcp") after the create; none → undecided with
  an inception_hint. New decide_project_inception(project_id, …) records or
  re-records; nothing given = an inherit-all decision, stated.
- enter_project carries `inception` ONLY for the caller's own, undecided
  project: inception_ask() = the project's current defaults + what to ask the
  operator once + the exact call (the #2683 ask shape). Absent otherwise.
- REST: POST /api/projects accepts `inception` (validated before the create);
  POST /api/projects/<id>/inception decides/re-decides; GET …/inception/defaults
  is the card's payload; GET project already carries inception via to_dict.
- _INSTRUCTIONS: ORIENT names the ask; START a project names the questions —
  never create a project bare by default (product behaviour, P#119).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scribe/routes/projects.py

@@ -5,6 +5,7 @@ from quart import Blueprint, g, jsonify, request
 
 from scribe.auth import login_required, get_current_user_id
 from scribe.routes.utils import not_found, parse_pagination
+from scribe.services import inception as inception_svc
 from scribe.services.milestones import list_milestones
 from scribe.services.notes import list_notes
 from scribe.services.projects import (
@@ -66,6 +67,15 @@ async def create_project_route():
     status = data.get("status", "active")
     if status not in ("active", "paused", "completed", "archived"):
         return jsonify({"error": "status must be 'active', 'paused', 'completed', or 'archived'"}), 400
+    # The inception decision rides the create (milestone 297): the UI's
+    # second step sends `inception: {choices}`; absent = undecided, and the
+    # project page shows the card until it is. Validated before the create
+    # so a bad decision never leaves a half-made project behind.
+    inception = data.get("inception")
+    if inception is not None:
+        error = inception_svc.validate_inception(inception)
+        if error:
+            return jsonify({"error": error}), 400
     project = await create_project(
         uid,
         title=data["title"],
@@ -74,7 +84,44 @@ async def create_project_route():
         color=data.get("color"),
         status=status,
     )
-    return jsonify(project.to_dict()), 201
+    out = project.to_dict()
+    if inception is not None:
+        try:
+            decided = await inception_svc.decide(uid, project.id, choices=inception, via="ui")
+        except ValueError as exc:
+            return jsonify({"error": str(exc), "project": out}), 400
+        out["inception"] = decided["inception"]
+        out["inception_effects"] = decided["effects"]
+    return jsonify(out), 201
+
+
+@projects_bp.route("/<int:project_id>/inception", methods=["POST"])
+@login_required
+async def decide_inception_route(project_id: int):
+    """Record (or re-record) what a project inherits — milestone 297.
+    Body: the choices object {exclude_always_on_rulebooks, subscribe_rulebooks,
+    design_system_id, seed_systems}; owner-only."""
+    uid = get_current_user_id()
+    data = await request.get_json() or {}
+    choices = data.get("choices", data)
+    try:
+        decided = await inception_svc.decide(uid, project_id, choices=choices, via="ui")
+    except ValueError as exc:
+        msg = str(exc)
+        status = 404 if "not found" in msg else 400
+        return jsonify({"error": msg}), status
+    return jsonify({"project_id": project_id, **decided})
+
+
+@projects_bp.route("/<int:project_id>/inception/defaults", methods=["GET"])
+@login_required
+async def inception_defaults_route(project_id: int):
+    """What the project inherits if nobody decides — the card's payload."""
+    uid = get_current_user_id()
+    try:
+        return jsonify(await inception_svc.current_defaults(uid, project_id))
+    except ValueError:
+        return not_found("Project")
 
 
 @projects_bp.route("/<int:project_id>", methods=["GET"])