docs + clippy: drop the retired C-08 stub reference; cloned_ref_to_slice_refs

- websocket/upgrade.rs: OpenableAlpn's spec doc advertised the removed
  `channel:pub_open_not_implemented` stub (upstream C-08, fixed in
  alkcall with the single-publish fixes) — rewritten to the current
  contract: Pub-typed marked specs are refused loudly at registration
  by `register_openable_with_establisher`; marked pub openables route
  through `ChannelCore::register_pub_openable`. Also dropped the
  stale 'alkcall 0.6.0' version pin
- adapters/from_openapi.rs: clippy rust-1.99
  `cloned_ref_to_slice_refs` — std::slice::from_ref instead of a
  single-element to_string slice

Verified: cargo test (458 ok), clippy --all-targets -D warnings,
fmt --check

src/adapters/from_openapi.rs

@@ -465,7 +465,7 @@ impl FromOpenAPI {
                      `paths` for this path's `parameters` (and the path-item's shared \
                      list) has `name` and `in`, and that its $ref, if any, resolves. \
                      The placeholder would otherwise render as a literal `{{}}` path segment",
-                    bounded_join(&[path_template.to_string()]),
+                    bounded_join(std::slice::from_ref(&path_template)),
                     bounded_join(&unbound)
                 ),
             });

src/websocket/upgrade.rs

@@ -267,14 +267,17 @@ impl WsSessions {
 #[derive(Clone)]
 pub struct OpenableAlpn {
     /// The open-op spec (Query/Mutation/Sub with the `channel_open`
-    /// marker; a `Pub` open op resolves `channel:pub_open_not_implemented`
-    /// per the upstream C-08 stub until channel adoption lands).
+    /// marker). A `Pub`-typed marked spec is refused loudly at
+    /// registration by the upstream openable path (marked pub
+    /// openables register via alkcall's
+    /// `ChannelCore::register_pub_openable`, which this WS fork
+    /// wrapper does not thread yet).
     pub spec: OperationSpec,
     /// The data-plane protocol handler spawned on the allocated
     /// channel's `Connection` — `Fn(Value, Option<ChannelPlan>,
     /// Connection, AuthContext) -> JoinHandle<()>`. With an
-    /// establisher attached, the plan (alkcall 0.6.0 /
-    /// ADR-049 amendment 2) is the establisher's `Establishment.plan`:
+    /// establisher attached, the plan (alkcall ADR-049
+    /// amendment 2) is the establisher's `Establishment.plan`:
     /// the establisher and the handler agree on the concrete type
     /// (downcast in the ALPN crate); `None` when no establisher is
     /// registered or it returned `Establishment::default()`