feat: add preview tool — navigate + screenshot in one call with optional POST

New MCP tool `preview` combines goto + screenshot with viewport control.
Optionally POSTs result to any HTTP endpoint (e.g. HUD/visor) via previewUrl.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@saiden/browse",
-  "version": "0.3.3",
+  "version": "0.4.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@saiden/browse",
-      "version": "0.3.3",
+      "version": "0.4.0",
       "license": "BUSL-1.1",
       "dependencies": {
         "@modelcontextprotocol/sdk": "^1.26.0",