Implement bd stale command (bd-c01f, closes #184)

- Add bd stale command to find abandoned/forgotten issues
- Support --days (default 30), --status, --limit, --json flags
- Implement GetStaleIssues in SQLite and Memory storage
- Add full RPC/daemon support
- Comprehensive test suite (6 tests, all passing)
- Update AGENTS.md documentation

Resolves GitHub issue #184

Amp-Thread-ID: https://ampcode.com/threads/T-f021ddb8-54e3-41bf-ba7a-071749663c1d
Co-authored-by: Amp <amp@ampcode.com>

internal/rpc/client.go

@@ -265,6 +265,11 @@ func (c *Client) Ready(args *ReadyArgs) (*Response, error) {
 	return c.Execute(OpReady, args)
 }
 
+// Stale gets stale issues via the daemon
+func (c *Client) Stale(args *StaleArgs) (*Response, error) {
+	return c.Execute(OpStale, args)
+}
+
 // Stats gets statistics via the daemon
 func (c *Client) Stats() (*Response, error) {
 	return c.Execute(OpStats, nil)

internal/rpc/protocol.go

@@ -16,6 +16,7 @@ const (
 	OpList            = "list"
 	OpShow            = "show"
 	OpReady           = "ready"
+	OpStale           = "stale"
 	OpStats           = "stats"
 	OpDepAdd          = "dep_add"
 	OpDepRemove       = "dep_remove"
@@ -118,6 +119,13 @@ type ReadyArgs struct {
 	SortPolicy string `json:"sort_policy,omitempty"`
 }
 
+// StaleArgs represents arguments for the stale command
+type StaleArgs struct {
+	Days   int    `json:"days,omitempty"`
+	Status string `json:"status,omitempty"`
+	Limit  int    `json:"limit,omitempty"`
+}
+
 // DepAddArgs represents arguments for adding a dependency
 type DepAddArgs struct {
 	FromID  string `json:"from_id"`

internal/rpc/server_issues_epics.go

@@ -429,6 +429,39 @@ func (s *Server) handleReady(req *Request) Response {
 	}
 }
 
+func (s *Server) handleStale(req *Request) Response {
+	var staleArgs StaleArgs
+	if err := json.Unmarshal(req.Args, &staleArgs); err != nil {
+		return Response{
+			Success: false,
+			Error:   fmt.Sprintf("invalid stale args: %v", err),
+		}
+	}
+
+	store := s.storage
+
+	filter := types.StaleFilter{
+		Days:   staleArgs.Days,
+		Status: staleArgs.Status,
+		Limit:  staleArgs.Limit,
+	}
+
+	ctx := s.reqCtx(req)
+	issues, err := store.GetStaleIssues(ctx, filter)
+	if err != nil {
+		return Response{
+			Success: false,
+			Error:   fmt.Sprintf("failed to get stale issues: %v", err),
+		}
+	}
+
+	data, _ := json.Marshal(issues)
+	return Response{
+		Success: true,
+		Data:    data,
+	}
+}
+
 func (s *Server) handleStats(req *Request) Response {
 	store := s.storage
 

internal/rpc/server_routing_validation_diagnostics.go

@@ -172,6 +172,8 @@ func (s *Server) handleRequest(req *Request) Response {
 		resp = s.handleResolveID(req)
 	case OpReady:
 		resp = s.handleReady(req)
+	case OpStale:
+		resp = s.handleStale(req)
 	case OpStats:
 		resp = s.handleStats(req)
 	case OpDepAdd: