Port the shared table engine so the core matches JetBrains and Notepad++

CHANGELOG.md

@@ -4,6 +4,21 @@ All notable changes follow [Keep a Changelog](https://keepachangelog.com/en/1.1.
 
 ## [Unreleased]
 
+### Fixed
+
+- The table core is now a faithful port of the shared JetBrains/Notepad++ engine and matches it
+  byte for byte across the differential corpus. This corrects several behaviours that diverged:
+  - Prose that merely contains a pipe is no longer swallowed into the table and rewritten.
+  - Rows with more cells than the separator row grow the table instead of losing the extra cells.
+  - Deleting the row above the separator is refused, so a table can no longer lose its header.
+  - The caret lands on the cell content in right and centre aligned columns.
+  - Separator rows written with spaced dashes, `=` rules, or short `|---` lines are recognised.
+  - A pipe block without a separator row is no longer treated as a table.
+  - Fitting a width unwraps earlier continuation rows, so repeating the command is stable.
+  - Narrow and widen follow the content width instead of a fixed three column floor.
+  - CSV and TSV cells keep their internal whitespace, and new tables carry `Column N` headers.
+  - Display widths use the shared Unicode tables rather than the host runtime's Unicode data.
+
 ## [0.1.0] - 2026-08-04
 
 ### Added

e2e/extension.test.ts

@@ -30,11 +30,27 @@ test('extension activates and aligns an actual VS Code document', async () => {
   ].join('\n'));
 });
 
-test('next-cell command moves the real editor selection', async () => {
+test('next-cell command puts the caret on the content of a right aligned cell', async () => {
   editor.selection = new vscode.Selection(2, 2, 2, 2);
   await vscode.commands.executeCommand('markdownTableEditor.nextCell');
   assert.equal(editor.selection.active.line, 2);
-  assert.ok(editor.selection.active.character > 7);
+  const line = document.lineAt(2).text;
+  assert.equal(line, '| Анна |     2 |');
+  assert.equal(editor.selection.active.character, 13);
+  assert.equal(line[editor.selection.active.character], '2');
+});
+
+test('aligning never rewrites prose that follows the table', async () => {
+  const prose = await vscode.workspace.openTextDocument({
+    language: 'markdown',
+    content: '| A | B |\n| --- | --- |\n| x | y |\nSome prose | with a pipe',
+  });
+  const proseEditor = await vscode.window.showTextDocument(prose);
+  proseEditor.selection = new vscode.Selection(2, 2, 2, 2);
+  await vscode.commands.executeCommand('markdownTableEditor.align');
+  assert.equal(prose.getText(), '| A   | B   |\n| --- | --- |\n| x   | y   |\nSome prose | with a pipe');
+  await vscode.commands.executeCommand('workbench.action.closeActiveEditor');
+  editor = await vscode.window.showTextDocument(document);
 });
 
 test('CSV conversion edits the selected document range', async () => {