feat: add elaboration_input field to tasks for richer subtask placeholder

- Add ElaborationInput field to Task struct (task.go)
- Add DB migration and update CREATE/SELECT/scan in storage/db.go
- Update handleCreateTask to accept elaboration_input from API
- Update renderSubtaskRollup in app.js to prefer elaboration_input over description
- Capture elaborate prompt in createTask() form submission
- Update subtask-placeholder tests to cover elaboration_input priority
- Fix missing io import in gemini.go

When a task card is waiting for subtasks, it now shows:
  1. The raw user prompt from elaboration (if stored)
  2. The task description truncated at word boundary (~120 chars)
  3. The task name as fallback
  4. 'Waiting for subtasks…' only when all fields are empty

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/web/app.js b/web/app.js
index 408ffce..0e13543 100644
--- a/web/app.js
+++ b/web/app.js
@@ -883,7 +883,7 @@ async function renderSubtaskRollup(task, footer) {
     const res = await fetch(`${API_BASE}/api/tasks/${task.id}/subtasks`);
     const subtasks = await res.json();
     if (!subtasks || subtasks.length === 0) {
-      const blurb = task.description || task.name;
+      const blurb = task.elaboration_input || task.description || task.name;
       container.textContent = blurb ? truncateToWordBoundary(blurb) : 'Waiting for subtasks…';
       return;
     }
@@ -1555,9 +1555,12 @@ async function createTask(formData) {
   const workingDir = selectVal === '__new__'
     ? document.getElementById('new-project-input').value.trim()
     : selectVal;
+  const elaboratePromptEl = document.getElementById('elaborate-prompt');
+  const elaborationInput = elaboratePromptEl ? elaboratePromptEl.value.trim() : '';
   const body = {
     name: formData.get('name'),
     description: '',
+    elaboration_input: elaborationInput || undefined,
     agent: {
       instructions: formData.get('instructions'),
       project_dir: workingDir,