record where the member story actually stands

The platform now has `scope: 'shared'` for a dependency every account must be able to run, and the
check that goes with it — world-executable, and every parent directory traversable.

iris cannot use it yet, for a reason worth writing down rather than rediscovering: it BUILDS its
binary in the sidecar rather than declaring it as a dependency, so there is nothing for the probe to
judge. The remaining half is this sidecar installing into /usr/local/bin.

Also corrected open item 3, which said a member's agent "cannot read it there". On alpha it can —
/home/<owner> is mode 751, so an absolute path traverses. That is an accident, not a design, and 750
would break it silently. Stated that way so nobody concludes it already works.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

manifest.ts

@@ -47,6 +47,8 @@ export const manifest: PluginManifest = {
 
   osDependencies: [
     {
+      // Owner-scoped: cargo is the BUILDER, run once by this sidecar as the owner. Members never invoke
+      // it. What they need is the binary it produces — see the iris entry below.
       binary: 'cargo',
       reason:
         'Builds the iris screenshot binary from source, once, on first start. Nothing works without the build. ' +