feat(fs): bind external scopes to current execution lineage

Add fail-closed Composition lifetime attestation for non-root scopes; preserve pinned deployment-root semantics and principal visibility. Fetch and dispatch bind optional published scope refs inside the refreshed backend boundary.

Validation: cargo test -p wip-fs-server (25 unit, 8 HTTP, 31 extension tests and 1 doc-test); Nix clippy for FS and public example with -D warnings; git diff --check.

crates/wip-fs-server/tests/extensions.rs

@@ -125,6 +125,7 @@ struct Seen {
 #[derive(Default)]
 struct Controls {
     bump_before_execute: bool,
+    bump_ancestor: Option<String>,
     hide_before_execute: bool,
     hide_ancestor: Option<String>,
     replace_ancestor: Option<String>,
@@ -289,6 +290,9 @@ impl FilesystemBackend for MemoryBackend {
             entry.node.data.lock().unwrap().revision += 1;
             controls.bump_before_execute = false;
         }
+        if let Some(path) = controls.bump_ancestor.take() {
+            self.0.node(&path).data.lock().unwrap().revision += 1;
+        }
         if controls.hide_before_execute {
             entry.node.data.lock().unwrap().hidden = true;
         }
@@ -2188,8 +2192,11 @@ fn root_scope_replacement_during_call_rejects_the_prelookup() {
     );
 }
 
+#[path = "support/scoped.rs"]
+mod scoped;
+
 #[test]
-fn nonroot_registrations_fail_closed_until_the_engine_can_attest_their_lifetimes() {
+fn nonroot_registrations_fail_closed_without_composition_lifetime_attestation() {
     let fixture = Fixture::new();
     let mut registry = InterfaceRegistry::new();
     let root = Scope::new("/").unwrap();