Fix CRLF line endings, harden install.sh

- Add .gitattributes enforcing LF line endings
- Renormalize all files from CRLF to LF
- Replace fragile sed-based JSON manipulation with node -e
- Add Node.js 18+ version check (required for built-in fetch)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,13 +1,13 @@
-{
-  "name": "claude-statusline",
-  "version": "0.1.0",
-  "description": "Standalone Claude Code statusline for headless Linux servers",
-  "main": "statusline.js",
-  "scripts": {
-    "statusline": "node statusline.js",
-    "fetch": "node fetch-usage.js",
-    "install-statusline": "bash install.sh"
-  },
-  "keywords": ["claude", "statusline", "cli"],
-  "license": "MIT"
-}
+{
+  "name": "claude-statusline",
+  "version": "0.1.0",
+  "description": "Standalone Claude Code statusline for headless Linux servers",
+  "main": "statusline.js",
+  "scripts": {
+    "statusline": "node statusline.js",
+    "fetch": "node fetch-usage.js",
+    "install-statusline": "bash install.sh"
+  },
+  "keywords": ["claude", "statusline", "cli"],
+  "license": "MIT"
+}