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_grimoire_marker.py

@@ -65,7 +65,7 @@ def test_a_bare_integer_is_a_valid_marker(tmp_path):
 
 
 def test_the_marker_is_found_from_a_subdirectory(tmp_path):
-    _marker(tmp_path, instance=INSTANCE, project_id=2, project="FabledScribe")
+    _marker(tmp_path, instance=INSTANCE, project_id=2, project="FabledGrimoire")
     deep = tmp_path / "src" / "grimoire" / "services"
     deep.mkdir(parents=True)
     assert _sh(f'grimoire_scope_query "{deep}"', tmp_path) == "project_id=2"