Baseline: Ludic compiler + toolchain, Phase 1 syntax fixes complete

Self-hosted compiler (selfhost/*.ludic), runtime, examples, editor tooling,
and docs. Phase 1 of the syntax-redesign cohesion pass has landed:
edge-system fix, signature-query, when-alias, and the documentation truth-pass.
Suite green (14/14), C-free bootstrap fixpoint holds.

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

tools/editors/vscode/src/extension.js

@@ -0,0 +1,149 @@
+/* ============================================================================
+ * The VS Code half of Ludic support.
+ *
+ * There is deliberately very little here. Highlighting comes from the TextMate
+ * grammar in syntaxes/ (shared, unmodified, with every other editor), and
+ * everything else — completion, hover, diagnostics, formatting, symbols —
+ * comes from `ludic-lsp`, the same binary JetBrains and Neovim talk to. This
+ * file's whole job is finding that binary and keeping it alive.
+ * ==========================================================================*/
+const path = require('path');
+const fs = require('fs');
+const os = require('os');
+const vscode = require('vscode');
+const { LanguageClient, TransportKind } = require('vscode-languageclient/node');
+
+let client = null;
+let output = null;
+
+/** Where the language server might be, in the order we should look. */
+function resolveServer(folders) {
+  const configured = vscode.workspace.getConfiguration('ludic').get('server.path');
+  if (configured) return expand(configured);
+
+  const names = ['ludic-lsp', 'ludic-lsp.exe'];
+  for (const folder of folders) {
+    const root = folder.uri.fsPath;
+    for (const rel of ['build', 'tools/build', 'bin', '.']) {
+      for (const name of names) {
+        const p = path.join(root, rel, name);
+        if (isExecutable(p)) return p;
+      }
+    }
+  }
+  // Fall back to PATH; spawning by bare name lets the OS resolve it.
+  for (const dir of (process.env.PATH || '').split(path.delimiter)) {
+    for (const name of names) {
+      const p = path.join(dir, name);
+      if (isExecutable(p)) return p;
+    }
+  }
+  return null;
+}
+
+function resolveCompiler(folders) {
+  const configured = vscode.workspace.getConfiguration('ludic').get('compilerPath');
+  if (configured) return expand(configured);
+  for (const folder of folders) {
+    const p = path.join(folder.uri.fsPath, 'build', 'ludicc');
+    if (isExecutable(p)) return p;
+  }
+  return '';
+}
+
+function expand(p) {
+  return p.startsWith('~') ? path.join(os.homedir(), p.slice(1)) : p;
+}
+
+function isExecutable(p) {
+  try {
+    fs.accessSync(p, fs.constants.X_OK);
+    return fs.statSync(p).isFile();
+  } catch {
+    return false;
+  }
+}
+
+async function start(context) {
+  const cfg = vscode.workspace.getConfiguration('ludic');
+  if (!cfg.get('server.enabled')) return;
+
+  const folders = vscode.workspace.workspaceFolders || [];
+  const server = resolveServer(folders);
+  if (!server) {
+    // Not an error worth a modal: the grammar still highlights, and plenty of
+    // people open a .ludic file without having built the toolchain.
+    output.appendLine(
+      'ludic-lsp not found. Build it with tools/build-tools.sh, or set "ludic.server.path". ' +
+      'Syntax highlighting works without it; completion and diagnostics do not.'
+    );
+    return;
+  }
+  output.appendLine(`starting ${server}`);
+
+  const serverOptions = {
+    run: { command: server, args: ['--stdio'], transport: TransportKind.stdio },
+    debug: { command: server, args: ['--stdio'], transport: TransportKind.stdio }
+  };
+
+  const clientOptions = {
+    // Markdown is included on purpose: ```ludic fences in a .md get the same
+    // diagnostics, hover and semantic highlighting as a real source file.
+    documentSelector: [
+      { scheme: 'file', language: 'ludic' },
+      { scheme: 'file', language: 'markdown' }
+    ],
+    synchronize: {
+      fileEvents: vscode.workspace.createFileSystemWatcher('**/*.ludic'),
+      configurationSection: 'ludic'
+    },
+    outputChannel: output,
+    initializationOptions: {
+      compilerPath: resolveCompiler(folders),
+      compilerDiagnostics: cfg.get('compilerDiagnostics'),
+      indentSize: cfg.get('indentSize')
+    }
+  };
+
+  client = new LanguageClient('ludic', 'Ludic Language Server', serverOptions, clientOptions);
+  await client.start();
+  context.subscriptions.push(client);
+}
+
+async function stop() {
+  if (!client) return;
+  const c = client;
+  client = null;
+  await c.stop();
+}
+
+async function activate(context) {
+  output = vscode.window.createOutputChannel('Ludic');
+  context.subscriptions.push(output);
+
+  context.subscriptions.push(
+    vscode.commands.registerCommand('ludic.restartServer', async () => {
+      await stop();
+      await start(context);
+      vscode.window.setStatusBarMessage('Ludic: language server restarted', 3000);
+    }),
+    vscode.commands.registerCommand('ludic.showOutput', () => output.show())
+  );
+
+  context.subscriptions.push(
+    vscode.workspace.onDidChangeConfiguration(async (e) => {
+      if (e.affectsConfiguration('ludic.server')) {
+        await stop();
+        await start(context);
+      }
+    })
+  );
+
+  await start(context);
+}
+
+function deactivate() {
+  return stop();
+}
+
+module.exports = { activate, deactivate };