fix: plugin cannot be installed — manifest path, deps, and install script

- manifest.json: fix 'main' from 'src/main.js' to 'dist/main.js'
  (TypeScript compiles to dist/, not src/ — Obsidian could not find the entry point)
- manifest.json: set isDesktopOnly to true (plugin requires a local Ollama server)
- package.json: remove unused node-fetch dependency (ESM-only, conflicts with CommonJS build)
- src/semantic-cache.ts: use dynamic import for chromadb instead of top-level import
  (prevents plugin load crash when chromadb is not installed; cache defaults to disabled)
- install.sh: new script that installs deps, builds, and copies the plugin into a vault
- README.md: add quick install, manual install, and expanded troubleshooting sections

package.json

@@ -33,7 +33,6 @@
   },
   "dependencies": {
     "chromadb": "^1.5.3",
-    "node-fetch": "^3.3.2",
     "obsidian": "^1.4.11"
   }
 }