feat(memory): integrate vault into agent system

Register memory_save, memory_search, memory_recall tools in agent instance.
Update GetMemoryContext() to prefer vault _index.md over legacy MEMORY.md
with automatic truncation for large indexes. Update system prompt to
reference vault tools instead of raw MEMORY.md editing.

pkg/agent/context.go

@@ -68,7 +68,8 @@ You are picoclaw, a helpful AI assistant.
 
 ## Workspace
 Your workspace is at: %s
-- Memory: %s/memory/MEMORY.md
+- Memory Vault: %s/memory/ (use memory_save, memory_search, memory_recall tools)
+- Vault Index: %s/memory/_index.md (auto-generated)
 - Daily Notes: %s/memory/YYYYMM/YYYYMMDD.md
 - Skills: %s/skills/{skill-name}/SKILL.md
 
@@ -80,8 +81,8 @@ Your workspace is at: %s
 
 2. **Be helpful and accurate** - When using tools, briefly explain what you're doing.
 
-3. **Memory** - When interacting with me if something seems memorable, update %s/memory/MEMORY.md`,
+3. **Memory** - When something seems memorable, use the memory_save tool to save structured notes with tags. Use memory_recall to retrieve past knowledge.`,
-		now, runtime, workspacePath, workspacePath, workspacePath, workspacePath, toolsSection, workspacePath)
+		now, runtime, workspacePath, workspacePath, workspacePath, workspacePath, workspacePath, toolsSection)
 }
 
 func (cb *ContextBuilder) buildToolsSection() string {

pkg/agent/instance.go

@@ -6,6 +6,7 @@ import (
 	"strings"
 
 	"github.com/sipeed/picoclaw/pkg/config"
+	"github.com/sipeed/picoclaw/pkg/memory"
 	"github.com/sipeed/picoclaw/pkg/providers"
 	"github.com/sipeed/picoclaw/pkg/routing"
 	"github.com/sipeed/picoclaw/pkg/session"
@@ -55,6 +56,12 @@ func NewAgentInstance(
 	toolsRegistry.Register(tools.NewEditFileTool(workspace, restrict))
 	toolsRegistry.Register(tools.NewAppendFileTool(workspace, restrict))
 
+	// Memory vault tools
+	memVault := memory.NewVault(filepath.Join(workspace, "memory"))
+	toolsRegistry.Register(tools.NewMemorySaveTool(memVault))
+	toolsRegistry.Register(tools.NewMemorySearchTool(memVault))
+	toolsRegistry.Register(tools.NewMemoryRecallTool(memVault))
+
 	// Configure security middleware from config
 	if cfg != nil {
 		sec := cfg.Tools.Security

pkg/agent/memory.go

@@ -12,15 +12,18 @@ import (
 	"path/filepath"
 	"strings"
 	"time"
+
+	"github.com/sipeed/picoclaw/pkg/memory"
 )
 
 // MemoryStore manages persistent memory for the agent.
-// - Long-term memory: memory/MEMORY.md
+// It supports both the legacy MEMORY.md format and the new vault-based
-// - Daily notes: memory/YYYYMM/YYYYMMDD.md
+// index system. When a vault _index.md exists, it is preferred over MEMORY.md.
 type MemoryStore struct {
 	workspace  string
 	memoryDir  string
 	memoryFile string
+	vault      *memory.Vault
 }
 
 // NewMemoryStore creates a new MemoryStore with the given workspace path.
@@ -36,6 +39,7 @@ func NewMemoryStore(workspace string) *MemoryStore {
 		workspace:  workspace,
 		memoryDir:  memoryDir,
 		memoryFile: memoryFile,
+		vault:      memory.NewVault(memoryDir),
 	}
 }
 
@@ -123,24 +127,40 @@ func (ms *MemoryStore) GetRecentDailyNotes(days int) string {
 }
 
 // GetMemoryContext returns formatted memory context for the agent prompt.
-// Includes long-term memory and recent daily notes.
+// Prefers the vault index (_index.md) when available, falling back to
+// the legacy MEMORY.md. Recent daily notes are always included.
 func (ms *MemoryStore) GetMemoryContext() string {
-	longTerm := ms.ReadLongTerm()
+	// Prefer vault index over legacy MEMORY.md
+	index := ms.vault.ReadIndex()
+	if index == "" {
+		index = ms.ReadLongTerm()
+	}
+
 	recentNotes := ms.GetRecentDailyNotes(3)
 
-	if longTerm == "" && recentNotes == "" {
+	if index == "" && recentNotes == "" {
 		return ""
 	}
 
 	var sb strings.Builder
 
-	if longTerm != "" {
+	if index != "" {
-		sb.WriteString("## Long-term Memory\n\n")
+		sb.WriteString("## Memory Vault Index\n\n")
-		sb.WriteString(longTerm)
+		// Truncate if too large for system prompt
+		if len(index) > 4000 {
+			if tableEnd := strings.Index(index, "\n## Tags"); tableEnd > 0 {
+				sb.WriteString(index[:tableEnd])
+			} else {
+				sb.WriteString(index[:4000])
+				sb.WriteString("\n\n(Index truncated. Use memory_search for full details.)")
+			}
+		} else {
+			sb.WriteString(index)
+		}
 	}
 
 	if recentNotes != "" {
-		if longTerm != "" {
+		if index != "" {
 			sb.WriteString("\n\n---\n\n")
 		}
 		sb.WriteString("## Recent Daily Notes\n\n")