feat(inception): UI — New-project modal step 2, InceptionCard on the project page, Rules tab shows excluded always-on rulebooks; REST exclusion routes (#2883, milestone 297 step 5)

- components/InceptionCard.vue: the one form, two homes — mode="create" in
  the New-project modal's second step (emits the choices; the create carries
  `inception`), mode="decide" on ProjectView for the owner of an undecided
  project (loads that project's defaults, records the decision). Always-on
  rulebooks listed checked (uncheck = exclude), others unchecked (check =
  subscribe), design system select, seed-Systems toggle (disabled once the
  project has Systems). Tokens only; modal canon (#2855); .btn-* canon.
- ProjectView: the card while undecided, one "Inheritance decided <date> via
  … · …" line after; onDecided refreshes the project.
- ProjectRulesTab: "Excluded always-on rulebooks" section with include-back.
- api/inception.ts (types, fetchInceptionDefaults, decideInception);
  api/rulebooks.ts: ApplicableRules.excluded_always_on, exclude/include
  wrappers; REST POST/DELETE /api/projects/<id>/exclusions/rulebooks/<rb>.

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

src/scribe/routes/rulebooks.py

@@ -288,6 +288,32 @@ async def unsuppress_project_topic(project_id: int, topic_id: int):
     return "", 204
 
 
+@rulebooks_bp.post("/projects/<int:project_id>/exclusions/rulebooks/<int:rulebook_id>")
+@login_required
+async def exclude_project_rulebook(project_id: int, rulebook_id: int):
+    """Opt the project out of a whole always-on rulebook (milestone 297)."""
+    try:
+        await rulebooks_svc.exclude_always_on_rulebook_for_project(
+            project_id=project_id, rulebook_id=rulebook_id, user_id=get_current_user_id(),
+        )
+    except ValueError as exc:
+        msg = str(exc)
+        return jsonify({"error": msg}), (400 if "not always-on" in msg else 404)
+    return "", 204
+
+
+@rulebooks_bp.delete("/projects/<int:project_id>/exclusions/rulebooks/<int:rulebook_id>")
+@login_required
+async def include_project_rulebook(project_id: int, rulebook_id: int):
+    try:
+        await rulebooks_svc.include_always_on_rulebook_for_project(
+            project_id=project_id, rulebook_id=rulebook_id, user_id=get_current_user_id(),
+        )
+    except ValueError as exc:
+        return jsonify({"error": str(exc)}), 404
+    return "", 204
+
+
 @rulebooks_bp.post("/projects/<int:project_id>/rules")
 @login_required
 async def create_project_rule(project_id: int):