rename: cosmic-brain → claude-obsidian

Updates all references across README, CLAUDE.md, ATTRIBUTION.md,
WIKI.md, docs/install-guide.md, wiki/getting-started.md,
plugin.json, marketplace.json, commands/wiki.md, setup-vault.sh,
wiki pages, and renames wiki/meta/cosmic-brain-cover.gif.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

.obsidian/graph.json

@@ -67,6 +67,6 @@
   "repelStrength": 20,
   "linkStrength": 1,
   "linkDistance": 80,
-  "scale": 0.40700950846340656,
-  "close": false
+  "scale": 0.5191098990818888,
+  "close": true
 }