fix(export): render vimwiki-compatible HTML for templates, links, and tasks

Stock vimwiki templates and stylesheets rendered broken pages because the
HTML output diverged from vimwiki conventions on three fronts:

- Templates: the renderer only substituted nuwiki's `{{key}}` placeholders,
  so vimwiki's `%title%`/`%content%`/`%root_path%`/`%date%`/`%wiki_css%`
  passed through literally — dropping the body and breaking asset links.
  Both delimiter styles are now recognised; `%wiki_css%` aliases the css var.
- Links: `[[todo.wiki]]` exported to `todo.wiki.html`. render_page_html now
  takes the wiki file extension and strips it from wiki/interwiki targets
  (via index::strip_wiki_extension) before the `.html` URL is built, matching
  in-editor navigation. file:/local: links keep their literal extension.
- Tasks: checkbox items used bespoke `task-*` classes plus an `<input>`,
  which double-rendered against vimwiki stylesheets. Emit `done0..done4`
  (`[ ] [.] [o] [O] [X]`) and `rejected` (`[-]`) classes with no input — the
  stylesheet draws the box.

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

crates/nuwiki-lsp/src/export.rs

@@ -18,7 +18,7 @@
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 
-use nuwiki_core::ast::{BlockNode, DocumentNode, HeadingNode, InlineNode};
+use nuwiki_core::ast::{BlockNode, DocumentNode, HeadingNode, InlineNode, LinkKind};
 use nuwiki_core::date::DiaryDate;
 use nuwiki_core::render::{HtmlRenderer, Renderer};
 
@@ -188,12 +188,18 @@ pub fn is_excluded(patterns: &[String], name: &str) -> bool {
 /// Pure HTML render pass. The caller has already loaded the template
 /// (or falls back). Wires up `{{date}}`, `{{root_path}}`, `{{toc}}`
 /// plus arbitrary extras passed via `extra_vars`.
+///
+/// `wiki_extension` is the wiki's source file extension (e.g. `".wiki"`).
+/// When set, it is stripped from wiki/interwiki link targets so a link
+/// written with the extension (`[[todo.wiki]]`) exports to `todo.html`,
+/// matching how the LSP resolves the same link for in-editor navigation.
 pub fn render_page_html(
     doc: &DocumentNode,
     template: Option<String>,
     name: &str,
     today: DiaryDate,
     cfg: &HtmlConfig,
+    wiki_extension: Option<&str>,
     extra_vars: HashMap<String, String>,
 ) -> std::io::Result<String> {
     let date_str = match doc.metadata.date.as_deref() {
@@ -211,11 +217,30 @@ pub fn render_page_html(
     vars.insert("root_path".into(), root_path);
     vars.insert("toc".into(), toc);
     vars.insert("css".into(), cfg.css_name.clone());
+    // vimwiki names the stylesheet placeholder `%wiki_css%`; alias it so stock
+    // templates resolve. nuwiki's own templates use `{{css}}`.
+    vars.insert("wiki_css".into(), cfg.css_name.clone());
     for (k, v) in extra_vars {
         vars.insert(k, v);
     }
 
     let mut r = HtmlRenderer::new();
+    if let Some(ext) = wiki_extension.filter(|e| !e.trim_start_matches('.').is_empty()) {
+        // Strip the wiki extension from page links before the default resolver
+        // turns them into `.html` URLs, so `[[todo.wiki]]` → `todo.html` rather
+        // than `todo.wiki.html`. Only wiki/interwiki targets are touched;
+        // file:/local: paths keep their literal extension.
+        let ext = ext.to_string();
+        r = r.with_link_resolver(move |target| {
+            let mut t = target.clone();
+            if matches!(t.kind, LinkKind::Wiki | LinkKind::Interwiki) {
+                if let Some(p) = t.path.take() {
+                    t.path = Some(crate::index::strip_wiki_extension(&p, Some(&ext)).to_string());
+                }
+            }
+            nuwiki_core::render::html::default_link_resolver(&t)
+        });
+    }
     if let Some(t) = template {
         r = r.with_template(t);
     }