fix: add postinstall chmod for npm binary permissions (#43)

* fix: add postinstall chmod for npm binary permissions

* fix: report npm package version instead of compiled binary version

The --version flag now reports the version from package.json instead of the
version compiled into the Rust binary. This ensures the version matches what
was installed via npm, even when binaries are reused from previous releases.

* fix: bake version into binary at build time

Instead of hacking around the version in the Node.js wrapper script,
properly pass the version at build time via SANDBOX_AGENT_VERSION env var.

Changes:
- build.rs: Generate version.rs with VERSION constant from env var
- main.rs: Use generated version constant for clap --version
- Dockerfiles: Accept SANDBOX_AGENT_VERSION as build arg
- build.sh: Pass version as second argument to Docker builds
- release.yaml: Pass version to build script during CI
- Remove version hack from sdks/cli/bin/sandbox-agent wrapper

The version is now baked into the binary during the release build,
ensuring --version reports the correct npm package version.

sdks/cli/platforms/darwin-arm64/package.json

@@ -13,6 +13,9 @@
   "cpu": [
     "arm64"
   ],
+  "scripts": {
+    "postinstall": "chmod +x bin/sandbox-agent || true"
+  },
   "files": [
     "bin"
   ]

sdks/cli/platforms/darwin-x64/package.json

@@ -13,6 +13,9 @@
   "cpu": [
     "x64"
   ],
+  "scripts": {
+    "postinstall": "chmod +x bin/sandbox-agent || true"
+  },
   "files": [
     "bin"
   ]

sdks/cli/platforms/linux-x64/package.json

@@ -13,6 +13,9 @@
   "cpu": [
     "x64"
   ],
+  "scripts": {
+    "postinstall": "chmod +x bin/sandbox-agent || true"
+  },
   "files": [
     "bin"
   ]