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>

plugin/hooks/grimoire_defs.sh

@@ -1308,7 +1308,7 @@ grimoire_turn_fact() {
 # Nothing Grimoire should be holding goes in it.
 #
 #   {"instance": "https://grimoire.example.com", "project_id": 2,
-#    "project": "FabledScribe"}
+#    "project": "FabledGrimoire"}
 #
 #   instance    WHICH Grimoire the id belongs to, and the reason this file is
 #               not just a number. A project id means nothing on its own: id 2