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>

bin/setup-vault.sh

@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-# cosmic-brain vault setup script
+# claude-obsidian vault setup script
 # Run this ONCE before opening Obsidian for the first time.
 # Usage: bash bin/setup-vault.sh [optional: /path/to/vault]
 # Default: uses the directory where this script lives (the vault root)
@@ -10,7 +10,7 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 VAULT="${1:-$(dirname "$SCRIPT_DIR")}"
 OBSIDIAN="$VAULT/.obsidian"
 
-echo "Setting up cosmic-brain vault at: $VAULT"
+echo "Setting up claude-obsidian vault at: $VAULT"
 
 # ── 1. Create directories ─────────────────────────────────────────────────────
 mkdir -p "$OBSIDIAN/snippets"