Remove stale phase/spec references from code comments

Strip "Phase N", "SPEC §X.Y", and "v1.x" planning labels from comments
across the Rust crates and editor layers now that those tracking
artifacts are gone. Comments only — no logic, strings, or test names
touched.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/nuwiki-core/tests/syntax.rs

@@ -136,7 +136,7 @@ fn registry_can_parse_through_trait_object() {
 }
 
 /// Compile-time check: SyntaxRegistry must be Send + Sync so the LSP server
-/// can share it across handler tasks (SPEC.md §6.3).
+/// can share it across handler tasks.
 #[test]
 fn registry_is_send_and_sync() {
     fn assert_send_sync<T: Send + Sync>() {}