feat(13.1-C): link helpers — pasteWikilink, pasteUrl, normalize

Closing out §13.1's smallest cluster. Three commands move from
"not yet implemented" stubs to real behaviour:

- `nuwiki.link.pasteWikilink` (server, executeCommand) — derives
  the current page name from the source URI + wiki root, returns a
  `WorkspaceEdit` inserting `[[<page>]]` at the requested cursor
  position.
- `nuwiki.link.pasteUrl` (server) — same lookup, but the inserted
  text is the page's relative HTML output URL
  (`<page>.html`, including subdir segments) so the snippet survives
  when the export root moves.
- `nuwiki.link.normalize` (client) — wraps the word at cursor as
  `[[word]]` without following. Reuses the `wrap_cword_as_wikilink`
  helper that already powers the `<CR>` two-step. Pure-VimL on the
  Vim path; pure-Lua on the Neovim path. No LSP round-trip.

Keymaps:
- `+` (normal + visual) now actually calls `normalize_link` on both
  editor paths instead of stubbing with a "deferred" notification.

Tests:
- 5 new Rust unit tests in `cluster_c_link_helpers.rs` covering
  command-list presence + the page-name derivation for root and
  subdirectory pages + the URL / wikilink shape strings.
- Neovim keymap harness gains a `links.normalize_via_+` case (20
  passing now, up from 19). Vim harness inherits the same
  command-presence check via its existing smoke tests.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/nuwiki-lsp/src/commands.rs

@@ -65,6 +65,8 @@ pub const COMMANDS: &[&str] = &[
     "nuwiki.wiki.openIndex",
     "nuwiki.wiki.tabOpenIndex",
     "nuwiki.wiki.gotoPage",
+    "nuwiki.link.pasteWikilink",
+    "nuwiki.link.pasteUrl",
 ];
 
 pub(crate) async fn execute(
@@ -155,6 +157,12 @@ pub(crate) async fn execute(
         "nuwiki.wiki.gotoPage" => {
             wiki_goto_page(backend, args).map(|o| o.map(CommandOutcome::Value))
         }
+        "nuwiki.link.pasteWikilink" => {
+            link_paste(backend, args, PasteKind::Wikilink).map(|o| o.map(CommandOutcome::Edit))
+        }
+        "nuwiki.link.pasteUrl" => {
+            link_paste(backend, args, PasteKind::Url).map(|o| o.map(CommandOutcome::Edit))
+        }
         other => Err(format!("unknown nuwiki command: {other}")),
     }
 }
@@ -688,6 +696,47 @@ fn wiki_open_index(
     })))
 }
 
+#[derive(Clone, Copy)]
+enum PasteKind {
+    Wikilink,
+    Url,
+}
+
+fn link_paste(
+    backend: &Backend,
+    args: Vec<Value>,
+    kind: PasteKind,
+) -> Result<Option<WorkspaceEdit>, String> {
+    let p = parse_pos(args)?;
+    let Some(wiki) = backend.wiki_for_uri(&p.uri) else {
+        return Ok(None);
+    };
+    let name = crate::index::page_name_from_uri(&p.uri, Some(&wiki.config.root));
+    if name.is_empty() {
+        return Ok(None);
+    }
+    let snippet = match kind {
+        PasteKind::Wikilink => format!("[[{name}]]"),
+        PasteKind::Url => {
+            // Mirror `export::output_path_for` — the URL is the path
+            // beneath `html_path`, relative to the *exported root*, so
+            // pasted links survive when the HTML output moves.
+            let mut url = String::new();
+            for (i, seg) in name.split('/').enumerate() {
+                if i > 0 {
+                    url.push('/');
+                }
+                url.push_str(seg);
+            }
+            url.push_str(".html");
+            url
+        }
+    };
+    let mut b = WorkspaceEditBuilder::new();
+    b.edit(p.uri, crate::edits::text_edit_insert(p.position, snippet));
+    Ok(Some(b.build()))
+}
+
 fn wiki_goto_page(backend: &Backend, args: Vec<Value>) -> Result<Option<Value>, String> {
     #[derive(Deserialize)]
     struct Args {