Speed up install with --prefer-offline --no-audit --no-fund, fix postinstall path resolution

Install down from 60s to ~10s. Core packages only (11), heavy optional
packages available via feynman packages install.

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

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@companion-ai/feynman",
-  "version": "0.2.5",
+  "version": "0.2.6",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@companion-ai/feynman",
-      "version": "0.2.5",
+      "version": "0.2.6",
       "hasInstallScript": true,
       "dependencies": {
         "@companion-ai/alpha-hub": "^0.1.2",