feat: D24 fact intervals (--as-of) and bin/stack assistant helpers.

Store valid_from/valid_to on leafs and filter search by calendar day without
overloading D16 source staleness; stack start/start-assistant wires brain + PicoClaw.

internal/httpapi/mcp.go

@@ -105,11 +105,18 @@ func (s *Server) mcpCall(r *http.Request, params json.RawMessage) (any, error) {
 		if limit < 1 || limit > 100 {
 			return mcpText(`{"error":"n must be int 1..100"}`, true), nil
 		}
+		asOf := ""
+		if raw, ok := p.Arguments["as_of"]; ok {
+			asOf = strings.TrimSpace(fmt.Sprint(raw))
+			if asOf == "<nil>" {
+				asOf = ""
+			}
+		}
 		if !s.tryAcquire(r) {
 			return nil, fmt.Errorf("cancelled")
 		}
 		defer s.release()
-		body, err = s.api.Search(r.Context(), q, limit)
+		body, err = s.api.Search(r.Context(), q, limit, asOf)
 	case "get":
 		id := strings.TrimSpace(fmt.Sprint(p.Arguments["id"]))
 		if id == "" || id == "<nil>" {

internal/httpapi/server.go

@@ -24,7 +24,7 @@ import (
 
 // API is the in-process brain surface. Production serve.go wires internal/brain.
 type API interface {
-	Search(ctx context.Context, query string, limit int) ([]byte, error)
+	Search(ctx context.Context, query string, limit int, asOf string) ([]byte, error)
 	Get(ctx context.Context, id string, body bool) ([]byte, error)
 	Stats(ctx context.Context) ([]byte, error)
 	Audit(ctx context.Context) ([]byte, error)
@@ -85,11 +85,12 @@ func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
 		}
 		limit = n
 	}
+	asOf := strings.TrimSpace(r.URL.Query().Get("as_of"))
 	if !s.acquire(w, r) {
 		return
 	}
 	defer s.release()
-	body, err := s.api.Search(r.Context(), q, limit)
+	body, err := s.api.Search(r.Context(), q, limit, asOf)
 	writeAPI(w, body, err)
 }
 
@@ -187,13 +188,18 @@ type ExecSearcher struct {
 	Timeout time.Duration
 }
 
-func (b ExecSearcher) Search(ctx context.Context, query string, limit int) ([]byte, error) {
+func (b ExecSearcher) Search(ctx context.Context, query string, limit int, asOf string) ([]byte, error) {
 	if b.Timeout == 0 {
 		b.Timeout = 60 * time.Second
 	}
 	ctx, cancel := context.WithTimeout(ctx, b.Timeout)
 	defer cancel()
-	cmd := exec.CommandContext(ctx, b.CmdPath, "--json", "-n", strconv.Itoa(limit), query)
+	args := []string{"--json", "-n", strconv.Itoa(limit)}
+	if asOf != "" {
+		args = append(args, "--as-of", asOf)
+	}
+	args = append(args, query)
+	cmd := exec.CommandContext(ctx, b.CmdPath, args...)
 	out, err := cmd.Output()
 	if err != nil {
 		var exitErr *exec.ExitError

internal/httpapi/server_test.go

@@ -21,10 +21,10 @@ type fakeSearcher struct {
 	calls    int
 	active   atomic.Int32
 	maxSeen  atomic.Int32
-	callback func(q string, limit int) ([]byte, error)
+	callback func(q string, limit int, asOf string) ([]byte, error)
 }
 
-func (f *fakeSearcher) Search(ctx context.Context, query string, limit int) ([]byte, error) {
+func (f *fakeSearcher) Search(ctx context.Context, query string, limit int, asOf string) ([]byte, error) {
 	f.mu.Lock()
 	f.calls++
 	f.mu.Unlock()
@@ -44,7 +44,7 @@ func (f *fakeSearcher) Search(ctx context.Context, query string, limit int) ([]b
 		}
 	}
 	if f.callback != nil {
-		return f.callback(query, limit)
+		return f.callback(query, limit, asOf)
 	}
 	return []byte(`{"query":"` + query + `","count":0,"results":[]}`), nil
 }
@@ -109,7 +109,7 @@ func TestSearchMissingQuery(t *testing.T) {
 }
 
 func TestSearchReturnsSearcherResult(t *testing.T) {
-	fs := &fakeSearcher{callback: func(q string, limit int) ([]byte, error) {
+	fs := &fakeSearcher{callback: func(q string, limit int, asOf string) ([]byte, error) {
 		return []byte(`{"query":"` + q + `","count":1,"results":[{"id":"x"}]}`), nil
 	}}
 	h := NewServer(fs, 1)
@@ -168,7 +168,7 @@ func TestSearchRejectsBadLimit(t *testing.T) {
 }
 
 func TestGetLeaf(t *testing.T) {
-	fs := &fakeSearcher{callback: func(q string, limit int) ([]byte, error) {
+	fs := &fakeSearcher{callback: func(q string, limit int, asOf string) ([]byte, error) {
 		return []byte(`{}`), nil
 	}}
 	h := NewServer(fs, 1)

internal/httpapi/spec.go

@@ -35,6 +35,7 @@ var Ops = []Op{
 		Params: []Param{
 			{Name: "q", In: "query", Type: "string", Description: "search query", Required: true},
 			{Name: "n", In: "query", Type: "integer", Description: "hit limit 1..100 (default 10)"},
+			{Name: "as_of", In: "query", Type: "string", Description: "YYYY-MM-DD; keep facts active on that day (D24)"},
 		},
 	},
 	{
@@ -54,6 +55,8 @@ var Ops = []Op{
 			{Name: "text", In: "query", Type: "string", Description: "leaf text (omit for CLI hint)"},
 			{Name: "root", In: "query", Type: "string", Description: "facts or info (default info)"},
 			{Name: "source", In: "query", Type: "string", Description: "evidence pointer; facts need two sources"},
+			{Name: "valid_from", In: "query", Type: "string", Description: "fact interval start YYYY-MM-DD (D24)"},
+			{Name: "valid_to", In: "query", Type: "string", Description: "fact interval end YYYY-MM-DD inclusive (D24)"},
 		},
 	},
 	{Path: PathOpenAPI, Method: "get", ID: "openapi", Summary: "OpenAPI 3 document for this server"},