fix(operations): per-project git sync + completion receipts in brief (S2, S3)

Brief.Git was a single GitSync read from ORCHESTRA_DATA (never a git
checkout), and completions were counted but discarded their report_ref/
receipt. Brief.Git is now keyed by project ID and built from each
project's real repo; GitSync gained Ahead/Behind vs upstream; Brief now
carries Receipts pulled from each TaskCompleted payload.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1rkJ2hBMybnJctPbcy4tT

cmd/orchestra/main.go

@@ -363,7 +363,19 @@ func main() {
 		if v, parseErr := time.Parse(time.RFC3339, r.URL.Query().Get("to")); parseErr == nil {
 			to = v
 		}
-		json.NewEncoder(w).Encode(operations.BuildBrief(s.Events(0), from, to, operations.GitState(dir)))
+		git := map[string]operations.GitSync{}
+		for _, p := range rr.Projects() {
+			if p.Repo == "" {
+				continue
+			}
+			git[p.ID] = operations.GitState(p.Repo)
+		}
+		if len(git) == 0 {
+			if repo := os.Getenv("ORCHESTRA_REPO"); repo != "" {
+				git["default"] = operations.GitState(repo)
+			}
+		}
+		json.NewEncoder(w).Encode(operations.BuildBrief(s.Events(0), from, to, git))
 	})
 	standup := func() (domain.Event, error) {
 		return operations.GenerateStandupAdvisory(s, time.Now().UTC())