add gitignore and commit Obsidian vault config

Exclude .env (a GOOGLE_CLOUD_PROJECT value was present at the repo root),
.claude/settings.local.json, OS cruft, and personal Obsidian workspace
state (workspace.json, workspace-mobile.json, cache). Commit the rest of
.obsidian/ so the vault reopens with the same plugins, graph settings,
and daily-notes config on any machine.

Also expand Obsidian's userIgnoreFilters so .claude, .env, and .gitignore
don't pollute the file explorer, search, or graph view.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.obsidian/core-plugins.json

@@ -0,0 +1,33 @@
+{
+  "file-explorer": true,
+  "global-search": true,
+  "switcher": true,
+  "graph": true,
+  "backlink": true,
+  "canvas": true,
+  "outgoing-link": true,
+  "tag-pane": true,
+  "footnotes": false,
+  "properties": true,
+  "page-preview": true,
+  "daily-notes": true,
+  "templates": true,
+  "note-composer": true,
+  "command-palette": true,
+  "slash-command": false,
+  "editor-status": true,
+  "bookmarks": true,
+  "markdown-importer": false,
+  "zk-prefixer": false,
+  "random-note": false,
+  "outline": true,
+  "word-count": true,
+  "slides": false,
+  "audio-recorder": false,
+  "workspaces": false,
+  "file-recovery": true,
+  "publish": false,
+  "sync": true,
+  "bases": true,
+  "webviewer": false
+}