rename(547): the repo is FabledGrimoire, and no stray "scribe" is left

The forge repo is now bvandeusen/FabledGrimoire. The plugin marketplace default,
the install commands in the docs and plugin README, the CI requirements title and
the example repo URLs in comments and tests follow it. docs/development.md now
names the image the build actually publishes, fabledgrimoire.

Two test names still said "scribes_own"; they now say "grimoires_own".

What still says scribe does so on purpose:
- the backup reader's accepted archive names and prefix;
- the label every stored secret is sealed under;
- the notes on keeping an old install's database names;
- the old migrations.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_services_plugin_context.py

@@ -111,7 +111,7 @@ async def test_build_session_context_includes_project_when_scoped():
     # design_system_id explicitly None: a bare MagicMock would hand back a truthy
     # auto-attribute and send this through the design branch, which is the
     # opposite of what this test is about.
-    project = MagicMock(id=2, title="FabledScribe", goal="ship it",
+    project = MagicMock(id=2, title="FabledGrimoire", goal="ship it",
                         design_system_id=None)
     with patch("grimoire.services.plugin_context.projects_svc.get_project",
                AsyncMock(return_value=project)), \
@@ -120,8 +120,8 @@ async def test_build_session_context_includes_project_when_scoped():
         from grimoire.services.plugin_context import build_session_context
         out = await build_session_context(user_id=7, project_id=2)
 
-    assert out["project"] == {"id": 2, "title": "FabledScribe"}
-    assert "## Active project: FabledScribe (id 2)" in out["context"]
+    assert out["project"] == {"id": 2, "title": "FabledGrimoire"}
+    assert "## Active project: FabledGrimoire (id 2)" in out["context"]
     assert "Open todo tasks: 4" in out["context"]
     # No design system on the project -> no design block at all. An install with
     # none is the ordinary case, not a degraded one.