feat(core): make checkbox lexing honor a configurable listsyms palette

Add a ListSyms type (vimwiki's g:vimwiki_listsyms) and thread it through
the lexer so checkbox glyphs are recognized from the configured palette
rather than the hardcoded ' .oOX'. Glyphs map to the existing five-bucket
CheckboxState, so the HTML renderer and AST consumers are unchanged.
VimwikiSyntax::parse_with_listsyms opts into a custom palette; the trait
parse() keeps the default.

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

crates/nuwiki-core/src/syntax/vimwiki/mod.rs

@@ -7,6 +7,7 @@ pub use lexer::{VimwikiLexer, VimwikiToken, VimwikiTokenKind};
 pub use parser::VimwikiParser;
 
 use crate::ast::DocumentNode;
+use crate::listsyms::ListSyms;
 use crate::syntax::{Lexer, Parser, SyntaxPlugin};
 
 /// SyntaxPlugin facade: chains `VimwikiLexer` + `VimwikiParser` so the
@@ -18,6 +19,15 @@ impl VimwikiSyntax {
     pub fn new() -> Self {
         Self
     }
+
+    /// Parse with a custom checkbox palette (vimwiki's `g:vimwiki_listsyms`).
+    /// The trait-level [`SyntaxPlugin::parse`] uses [`ListSyms::default`].
+    pub fn parse_with_listsyms(&self, text: &str, listsyms: &ListSyms) -> DocumentNode {
+        let tokens = VimwikiLexer::new()
+            .with_listsyms(listsyms.clone())
+            .lex(text);
+        VimwikiParser::new().parse(tokens)
+    }
 }
 
 impl SyntaxPlugin for VimwikiSyntax {