fix: stop tracking Obsidian user files, clean up .gitignore

- Remove redundant docs/README.md (already covered by /docs)
- Ignore entire .obsidian/ directory (user-specific workspace state)
- Remove all .obsidian files from git tracking

Made-with: Cursor

.gitignore

@@ -13,13 +13,8 @@ logs
 .fleet
 .idea
 
-# Obsidian vault (user-specific workspace settings)
-.obsidian/workspace.json
-.obsidian/workspace-mobile.json
-.obsidian/graph.json
-.obsidian/appearance.json
-.obsidian/cache/
-.obsidian/plugins/*/data.json
+# Obsidian vault (user-specific; never commit workspace state)
+.obsidian/
 conflict-files-obsidian-git.md
 .trash/
 
@@ -31,5 +26,3 @@ conflict-files-obsidian-git.md
 # Project docs (local only)
 /docs
 /migration
-docs/README.md
-content/articles/.obsidian/workspace.json