feat: make session creation a sequential workflow

- Refactor CreateSessionForm into step-by-step workflow
- Steps unlock sequentially: Project → Repository → Tool → Clone Mode → Branch
- Add visual step indicators with numbered badges
- Disable controls until prerequisites are met
- Add CSS for workflow step styling

apps/web/src/styles.css

@@ -2844,6 +2844,65 @@ a.nav-item,
   gap: var(--space-4);
 }
 
+/* Workflow Step Styles */
+.workflow-form {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-6);
+}
+
+.workflow-step {
+  opacity: 0.4;
+  pointer-events: none;
+  transition: opacity 0.2s ease;
+}
+
+.workflow-step.active {
+  opacity: 1;
+  pointer-events: auto;
+}
+
+.workflow-step.complete {
+  opacity: 0.7;
+  pointer-events: auto;
+}
+
+.workflow-step-header {
+  display: flex;
+  align-items: center;
+  gap: var(--space-3);
+  margin-bottom: var(--space-3);
+  font-weight: 600;
+  color: var(--text-muted);
+}
+
+.workflow-step.active .workflow-step-header {
+  color: var(--text-primary);
+}
+
+.workflow-step-number {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  width: 28px;
+  height: 28px;
+  border-radius: 50%;
+  background: var(--bg-muted);
+  color: var(--text-muted);
+  font-size: 14px;
+  font-weight: 600;
+}
+
+.workflow-step.active .workflow-step-number {
+  background: var(--primary);
+  color: white;
+}
+
+.workflow-step.complete .workflow-step-number {
+  background: var(--success);
+  color: white;
+}
+
 .status-badge {
   display: inline-flex;
   align-items: center;