chore: add pnpm packageManager field and workspace config

Add pnpm@10.33.0 as packageManager, create pnpm-workspace.yaml with
minimumReleaseAge (3 days) and onlyBuiltDependencies allowlist
(better-sqlite3, esbuild, protobufjs, sharp), update .npmrc as
safety-net fallback.

.npmrc

@@ -1 +1,3 @@
-minReleaseAge=7d
+# Safety net — pnpm-workspace.yaml has the authoritative minimumReleaseAge (4320 min = 3 days)
+# This .npmrc value is a fallback if npm is ever invoked directly
+minReleaseAge=3d

package.json

@@ -3,6 +3,7 @@
   "version": "1.2.52",
   "description": "Personal Claude assistant. Lightweight, secure, customizable.",
   "type": "module",
+  "packageManager": "pnpm@10.33.0",
   "main": "dist/index.js",
   "scripts": {
     "build": "tsc",

pnpm-workspace.yaml

@@ -0,0 +1,8 @@
+onlyBuiltDependencies:
+  - better-sqlite3
+  - esbuild
+  - protobufjs
+  - sharp
+
+pnpm:
+  minimumReleaseAge: 4320