Fix sidebar sections, terminal resize, and improve .gitignore

Sidebar:
- Add -webkit-user-select: none to section headers (WebKit prefix)
- Fix class mismatches: sidebar-section-chevron → section-chevron,
  sidebar-section-count → section-count, sidebar-section-list → sidebar-list

Terminal resize:
- Poll container dimensions after creation — retry fit every 50ms
  until container has non-zero width/height (up to 20 attempts)
- Add flex: 1 and min-height: 0 to .xterm inside session-panel
  so it participates in flex layout correctly

.gitignore:
- Comprehensive rewrite covering build output, Wails bindings,
  frontend libs, IDE files, OS metadata, and application data

.gitignore

@@ -1,36 +1,60 @@
-# Build output
-build/
+# ==========================================================================
+# Nexus Terminal — .gitignore
+# ==========================================================================
+
+# ── Build output ──────────────────────────────────────────────────────────
+build/bin/
+build/darwin/
+build/windows/
+build/linux/
 dist/
 
-# Dependencies
+# ── Go ────────────────────────────────────────────────────────────────────
 vendor/
-frontend/node_modules/
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+*.test
+*.out
+__debug_bin*
+coverage.out
+coverage.html
 
-# IDE
+# ── Frontend ──────────────────────────────────────────────────────────────
+frontend/node_modules/
+frontend/src/js/lib/
+
+# ── Wails auto-generated bindings (recreated on every build) ──────────────
+frontend/wailsjs/
+
+# ── IDE / editor ──────────────────────────────────────────────────────────
 .idea/
 .vscode/
 *.swp
 *.swo
 *~
+*.sublime-project
+*.sublime-workspace
+.project
+.classpath
+.settings/
 
-# OS
+# ── OS metadata ───────────────────────────────────────────────────────────
 .DS_Store
+.DS_Store?
+._*
 Thumbs.db
+ehthumbs.db
+Desktop.ini
+$RECYCLE.BIN/
 
-# Test
-coverage.out
-coverage.html
-
-# Binaries
-*.exe
-*.dll
-*.so
-*.dylib
-
-# Debug
-__debug_bin*
-
-# Application data (never commit)
+# ── Application data (never commit user data or secrets) ──────────────────
 *.db
 *.sqlite
+*.sqlite3
 vault.json
+*.pem
+*.key
+!build/appicon.png

frontend/src/css/sidebar.css

@@ -77,6 +77,7 @@
     letter-spacing: 0.06em;
     cursor: pointer;
     transition: color var(--transition-fast), background var(--transition-fast);
+    -webkit-user-select: none;
     user-select: none;
     text-align: left;
     background: none;

frontend/src/css/terminal.css

@@ -69,7 +69,9 @@
 /* xterm.js overrides for consistent look */
 .terminal-container .xterm,
 .session-panel .xterm {
+    flex: 1;
     height: 100%;
+    min-height: 0;
     padding: var(--space-1);
 }
 

frontend/src/js/sidebar.js

@@ -113,16 +113,16 @@ class Sidebar {
         // Section header
         const header = createElement('div', 'sidebar-section-header');
         header.innerHTML = `
-            <span class="sidebar-section-chevron ${isCollapsed ? 'collapsed' : ''}">${isCollapsed ? '▸' : '▾'}</span>
-            <span class="sidebar-section-title">${escapeHtml(title)}</span>
-            <span class="sidebar-section-count">${profiles.length}</span>
+            <span class="section-chevron ${isCollapsed ? 'collapsed' : ''}">${isCollapsed ? '▸' : '▾'}</span>
+            <span>${escapeHtml(title)}</span>
+            <span class="section-count">${profiles.length}</span>
         `;
         header.addEventListener('click', () => this.toggleSection(key));
         section.appendChild(header);
 
         // Items
         if (!isCollapsed) {
-            const list = createElement('div', 'sidebar-section-list');
+            const list = createElement('div', 'sidebar-list');
             for (const profile of profiles) {
                 list.appendChild(this.renderProfileItem(profile));
             }

frontend/src/js/terminal.js

@@ -67,14 +67,23 @@ class TerminalManager {
         const container = document.getElementById(containerId);
         term.open(container);
 
-        // Fit the terminal once the container has had time to lay out.
-        // A single requestAnimationFrame is not enough — the panel may
-        // still be transitioning from display:none, so we retry briefly.
+        // Fit the terminal once the container has real dimensions.
+        // The panel may have just transitioned from display:none, so we
+        // poll until the container reports a non-trivial size.
         const doFit = () => { try { fitAddon.fit(); } catch (_) { /* noop */ } };
-        requestAnimationFrame(doFit);
-        setTimeout(doFit, 50);
-        setTimeout(doFit, 150);
-        setTimeout(doFit, 400);
+        let fitAttempts = 0;
+        const tryFit = () => {
+            fitAttempts++;
+            const rect = container.getBoundingClientRect();
+            if (rect.width > 10 && rect.height > 10) {
+                doFit();
+            } else if (fitAttempts < 20) {
+                // Container still has no size — retry
+                setTimeout(tryFit, 50);
+                return;
+            }
+        };
+        requestAnimationFrame(tryFit);
 
         // Forward user keystrokes to the backend
         term.onData((data) => {