feat: Add interactive pre-flight checklists for ccw-loop and workflow-plan, including validation and task transformation steps

- Implemented `prep-loop.md` for ccw-loop, detailing source discovery, validation, task transformation, and auto-loop configuration.
- Created `prep-plan.md` for workflow planning, covering environment checks, task quality assessment, execution preferences, and final confirmation.
- Defined schemas and integration points for `prep-package.json` in both ccw-loop and workflow-plan skills, ensuring proper validation and task handling.
- Added error handling mechanisms for various scenarios during the preparation phases.

.codex/skills/workflow-plan-execute/phases/01-session-discovery.md

@@ -9,6 +9,79 @@ Discover existing sessions or start new workflow session with intelligent sessio
 - Generate unique session ID (WFS-xxx format)
 - Initialize session directory structure
 
+## Step 0.0: Load Prep Package (if exists)
+
+```javascript
+// Load plan-prep-package.json (generated by /prompts:prep-plan)
+let prepPackage = null
+const prepPath = `${projectRoot}/.workflow/.prep/plan-prep-package.json`
+
+if (fs.existsSync(prepPath)) {
+  const raw = JSON.parse(Read(prepPath))
+  const checks = validatePlanPrepPackage(raw, projectRoot)
+
+  if (checks.valid) {
+    prepPackage = raw
+    console.log(`✓ Prep package loaded: score=${prepPackage.task.quality_score}/10, exec=${prepPackage.execution.execution_method}`)
+    console.log(`  Checks passed: ${checks.passed.join(', ')}`)
+  } else {
+    console.warn(`⚠ Prep package found but failed validation:`)
+    checks.failures.forEach(f => console.warn(`  ✗ ${f}`))
+    console.warn(`  → Falling back to default behavior (prep-package ignored)`)
+    prepPackage = null
+  }
+}
+
+/**
+ * Validate plan-prep-package.json integrity before consumption.
+ */
+function validatePlanPrepPackage(prep, projectRoot) {
+  const passed = []
+  const failures = []
+
+  // Check 1: prep_status
+  if (prep.prep_status === 'ready') passed.push('status=ready')
+  else failures.push(`prep_status is "${prep.prep_status}", expected "ready"`)
+
+  // Check 2: target_skill
+  if (prep.target_skill === 'workflow-plan-execute') passed.push('target_skill match')
+  else failures.push(`target_skill is "${prep.target_skill}", expected "workflow-plan-execute"`)
+
+  // Check 3: project_root
+  if (prep.environment?.project_root === projectRoot) passed.push('project_root match')
+  else failures.push(`project_root mismatch: "${prep.environment?.project_root}" vs "${projectRoot}"`)
+
+  // Check 4: quality_score >= 6
+  if ((prep.task?.quality_score || 0) >= 6) passed.push(`quality=${prep.task.quality_score}/10`)
+  else failures.push(`quality_score ${prep.task?.quality_score || 0} < 6`)
+
+  // Check 5: generated_at within 24h
+  const hoursSince = (Date.now() - new Date(prep.generated_at).getTime()) / 3600000
+  if (hoursSince <= 24) passed.push(`age=${Math.round(hoursSince)}h`)
+  else failures.push(`prep-package is ${Math.round(hoursSince)}h old (max 24h)`)
+
+  // Check 6: required fields
+  const required = ['task.structured.goal', 'task.structured.scope', 'execution.execution_method']
+  const missing = required.filter(p => !p.split('.').reduce((o, k) => o?.[k], prep))
+  if (missing.length === 0) passed.push('fields complete')
+  else failures.push(`missing: ${missing.join(', ')}`)
+
+  return { valid: failures.length === 0, passed, failures }
+}
+
+// Build structured description from prep or raw input
+let structuredDescription
+if (prepPackage) {
+  structuredDescription = {
+    goal: prepPackage.task.structured.goal,
+    scope: prepPackage.task.structured.scope,
+    context: prepPackage.task.structured.context
+  }
+} else {
+  structuredDescription = null  // Will be parsed from user input later
+}
+```
+
 ## Step 0: Initialize Project State (First-time Only)
 
 **Executed before all modes** - Ensures project-level state files exist by calling `workflow:init`.
@@ -73,23 +146,47 @@ CONTEXT: Existing user database schema, REST API endpoints
 
 ### Step 1.4: Initialize Planning Notes
 
-Create `planning-notes.md` with N+1 context support:
+Create `planning-notes.md` with N+1 context support, enriched with prep data:
 
 ```javascript
 const planningNotesPath = `${projectRoot}/.workflow/active/${sessionId}/planning-notes.md`
-const userGoal = structuredDescription.goal
-const userConstraints = structuredDescription.context || "None specified"
+const userGoal = structuredDescription?.goal || taskDescription
+const userScope = structuredDescription?.scope || "Not specified"
+const userConstraints = structuredDescription?.context || "None specified"
+
+// Build source refs section from prep
+const sourceRefsSection = (prepPackage?.task?.source_refs?.length > 0)
+  ? prepPackage.task.source_refs
+    .filter(r => r.status === 'verified' || r.status === 'linked')
+    .map(r => `- **${r.type}**: ${r.path}`)
+    .join('\n')
+  : 'None'
+
+// Build quality dimensions section from prep
+const dimensionsSection = prepPackage?.task?.dimensions
+  ? Object.entries(prepPackage.task.dimensions)
+    .map(([k, v]) => `- **${k}**: ${v.value} (${v.score}/2)`)
+    .join('\n')
+  : ''
 
 Write(planningNotesPath, `# Planning Notes
 
 **Session**: ${sessionId}
 **Created**: ${new Date().toISOString()}
+${prepPackage ? `**Prep Package**: plan-prep-package.json (score: ${prepPackage.task.quality_score}/10)` : ''}
 
 ## User Intent (Phase 1)
 
 - **GOAL**: ${userGoal}
+- **SCOPE**: ${userScope}
 - **KEY_CONSTRAINTS**: ${userConstraints}
-
+${sourceRefsSection !== 'None' ? `
+### Requirement Sources (from prep)
+${sourceRefsSection}
+` : ''}${dimensionsSection ? `
+### Quality Dimensions (from prep)
+${dimensionsSection}
+` : ''}
 ---
 
 ## Context Findings (Phase 2)