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/src/ast/visit.rs

@@ -5,10 +5,10 @@
 //! Override any method to short-circuit or augment traversal — call the
 //! matching `walk_*` from your override to keep descending.
 //!
-//! Pattern follows `rustc`'s and `syn`'s visitors. See SPEC.md §6.4 + P4.
+//! Pattern follows `rustc`'s and `syn`'s visitors.
 //!
 //! Read-only for now. A `VisitorMut` flavor can be added when transformations
-//! become relevant (post-Phase 5).
+//! become relevant.
 
 use super::block::{
     BlockNode, BlockquoteNode, CommentNode, DefinitionItemNode, DefinitionListNode, ErrorNode,