feat(13.1-B): table rewriters — insert, align, moveColumn

Closes the table-rewriter cluster from SPEC §13.1.

Server-side (ops module):
- `render_blank_table(cols, rows)` — pure templating: header row,
  separator `|--|--|--|`, then `rows` empty data rows. Wired through
  `table_insert` which dispatches a `TextEdit` at the cursor.
- `table_align_edit` — locates the `TableNode` containing the cursor
  line, computes max width per column across every row, re-emits the
  table with each cell space-padded to its column's width. The
  parser drops `|---|---|` separator rows but sets
  `TableNode.has_header`; the renderer re-inserts a padded separator
  after the header so the result still parses.
- `table_move_column_edit` — column-under-cursor swap with the
  left or right neighbour (`dir = "left" | "right"`). Cursor column
  is computed by counting pipe separators before the cursor's byte
  offset on the row's line. Column widths swap alongside the data so
  the post-swap table stays aligned. No-ops cleanly when the swap
  would fall off either edge.

Editor glue:
- `lua/nuwiki/commands.lua` / `autoload/nuwiki/commands.vim` — the
  three "not yet implemented" stubs are replaced with real LSP
  dispatchers. `table_insert` accepts optional `cols`/`rows`
  arguments (defaults: 3×2).
- Default keymaps `gqq` / `gq1` / `gww` / `gw1` now call
  `table_align`; `<A-Left>` / `<A-Right>` call
  `table_move_column_left` / `_right`. No more "deferred"
  notifications on the table keys.

Tests: 8 new in `cluster_b_table_rewriters.rs` — blank-table shape
(3×2 + 1×1), column-width alignment with separator-row repad, swap-
right shape, swap-left clamp at column 0, no-table-found fallbacks,
COMMANDS list completeness. Total 410 Rust tests pass; clippy clean;
Neovim keymap harness still 20/20.

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

ftplugin/vimwiki.vim

@@ -181,13 +181,13 @@ if !has('nvim')
     nnoremap <silent><buffer> <Leader>whh  :call nuwiki#commands#export_browse()<CR>
     nnoremap <silent><buffer> <Leader>wha  :call nuwiki#commands#export_all()<CR>
 
-    " Tables (deferred §13.1)
-    nnoremap <silent><buffer> gqq        :echohl WarningMsg<bar>echom 'nuwiki: :VimwikiTableAlignQ not yet implemented — see SPEC §13.1'<bar>echohl None<CR>
-    nnoremap <silent><buffer> gq1        :echohl WarningMsg<bar>echom 'nuwiki: :VimwikiTableAlignQ1 not yet implemented — see SPEC §13.1'<bar>echohl None<CR>
-    nnoremap <silent><buffer> gww        :echohl WarningMsg<bar>echom 'nuwiki: :VimwikiTableAlignW not yet implemented — see SPEC §13.1'<bar>echohl None<CR>
-    nnoremap <silent><buffer> gw1        :echohl WarningMsg<bar>echom 'nuwiki: :VimwikiTableAlignW1 not yet implemented — see SPEC §13.1'<bar>echohl None<CR>
-    nnoremap <silent><buffer> <A-Left>   :echohl WarningMsg<bar>echom 'nuwiki: :VimwikiTableMoveColumnLeft not yet implemented'<bar>echohl None<CR>
-    nnoremap <silent><buffer> <A-Right>  :echohl WarningMsg<bar>echom 'nuwiki: :VimwikiTableMoveColumnRight not yet implemented'<bar>echohl None<CR>
+    " Tables
+    nnoremap <silent><buffer> gqq        :call nuwiki#commands#table_align()<CR>
+    nnoremap <silent><buffer> gq1        :call nuwiki#commands#table_align()<CR>
+    nnoremap <silent><buffer> gww        :call nuwiki#commands#table_align()<CR>
+    nnoremap <silent><buffer> gw1        :call nuwiki#commands#table_align()<CR>
+    nnoremap <silent><buffer> <A-Left>   :call nuwiki#commands#table_move_left()<CR>
+    nnoremap <silent><buffer> <A-Right>  :call nuwiki#commands#table_move_right()<CR>
   endif
 
   finish