feat: add code execution REPL with JS, Python, Bash support

src/repl/repl-panel.js

@@ -0,0 +1,49 @@
+class ReplPanel {
+    constructor() {
+        this.panel = document.getElementById('bottom-panel');
+        this.output = document.getElementById('repl-output');
+        this.setupEventListeners();
+    }
+
+    setupEventListeners() {
+        document.getElementById('bottom-panel-toggle')?.addEventListener('click', () => this.toggle());
+        document.getElementById('repl-clear')?.addEventListener('click', () => this.clear());
+    }
+
+    toggle() {
+        this.panel.classList.toggle('collapsed');
+        const btn = document.getElementById('bottom-panel-toggle');
+        if (btn) btn.textContent = this.panel.classList.contains('collapsed') ? '\u25BC' : '\u25B2';
+    }
+
+    show() {
+        this.panel.classList.remove('collapsed');
+        const btn = document.getElementById('bottom-panel-toggle');
+        if (btn) btn.textContent = '\u25B2';
+    }
+
+    clear() {
+        if (this.output) this.output.innerHTML = '';
+    }
+
+    appendOutput(command, result) {
+        const entry = document.createElement('div');
+        entry.className = 'repl-entry';
+        entry.innerHTML = `
+            <div class="repl-command">\u25B6 ${command}</div>
+            ${result.stdout ? `<div class="repl-stdout">${this.escapeHtml(result.stdout)}</div>` : ''}
+            ${result.stderr ? `<div class="repl-stderr">${this.escapeHtml(result.stderr)}</div>` : ''}
+            ${result.error ? `<div class="repl-error">Error: ${this.escapeHtml(result.error)}</div>` : ''}
+        `;
+        this.output?.appendChild(entry);
+        this.output?.scrollTo(0, this.output.scrollHeight);
+    }
+
+    escapeHtml(text) {
+        const div = document.createElement('div');
+        div.textContent = text;
+        return div.innerHTML;
+    }
+}
+
+module.exports = { ReplPanel };