feat: add teaching asset prompts

internal/teachingassets/store.go

@@ -0,0 +1,49 @@
+package teachingassets
+
+import (
+	"sync"
+
+	"tutor/internal/workflows"
+)
+
+type Store interface {
+	SavePrompt(PromptCandidate) (PromptCandidate, error)
+	Snapshot() Snapshot
+}
+
+type MemoryStore struct {
+	mu      sync.RWMutex
+	prompts []PromptCandidate
+}
+
+func NewMemoryStore() *MemoryStore {
+	return &MemoryStore{}
+}
+
+func (s *MemoryStore) SavePrompt(prompt PromptCandidate) (PromptCandidate, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	s.prompts = append(s.prompts, clonePrompt(prompt))
+	return prompt, nil
+}
+
+func (s *MemoryStore) Snapshot() Snapshot {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	return Snapshot{Prompts: clonePrompts(s.prompts)}
+}
+
+func clonePrompts(items []PromptCandidate) []PromptCandidate {
+	cloned := make([]PromptCandidate, len(items))
+	for i, item := range items {
+		cloned[i] = clonePrompt(item)
+	}
+	return cloned
+}
+
+func clonePrompt(prompt PromptCandidate) PromptCandidate {
+	prompt.SourceEvidence = append([]workflows.EvidenceRef(nil), prompt.SourceEvidence...)
+	return prompt
+}