feat(generate): insert links/tags sections at the cursor line too

Extend the cursor-line insertion from :NuwikiTOC to the other buffer
list generators: :NuwikiGenerateLinks and :NuwikiGenerateTagLinks. They
appended at end-of-file; a fresh section now goes at the cursor line
(with a leading blank), matching :NuwikiTOC. An existing section is still
refreshed in place, and the auto_generate_*-on-save hooks are unaffected
(they only ever replace).

Shared section_insert() helper computes the insert position/block for all
three (cursor line clamped to the document, else the per-command fallback:
top of file for TOC, EOF for links/tags). Clients send the 0-based cursor
line; handlers parse it via parse_uri_line_arg and thread it through
links_edit / tag_links_edit. Rebuild variants pass None.

Tests: links_edit_inserts_at_cursor_line + tag_links_edit_inserts_at_cursor_line.
577 passed, clippy clean, keymap harnesses green. Docs updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/nuwiki-lsp/tests/commands_coverage.rs

@@ -348,6 +348,7 @@ fn nuwiki_generate_links_lists_all_pages_excluding_current() {
         "Generated Links",
         1,
         0,
+        None,
         None
     )
     .is_some());
@@ -430,7 +431,8 @@ fn nuwiki_generate_tag_links_builds_section() {
         true,
         "Generated Tags",
         1,
-        0
+        0,
+        None
     )
     .is_some());
 }