feat(harness): dispatch /v1/harness/complete by harness kind (codex/opencode)

Adds an optional "harness" field so codex/opencode completions route to
their own Usage readers instead of always assuming Claude's transcript
format; unblocks the server side named as open in progress.md.

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

cmd/orchestra/main.go

@@ -260,6 +260,7 @@ func main() {
 		}
 		var p struct {
 			TaskID         string `json:"task_id"`
+			Harness        string `json:"harness"`
 			TranscriptPath string `json:"transcript_path"`
 			Report         string `json:"report"`
 		}
@@ -272,7 +273,23 @@ func main() {
 			http.Error(w, "task not found", http.StatusNotFound)
 			return
 		}
-		usage, err := herdr.ClaudeUsage(p.TranscriptPath)
+		// Harness-specific session-state readers (AUDIT.md "Codex/opencode
+		// completion producers"). Same local-filesystem assumption B3 already
+		// made for Claude: the caller supplies the path to its own session
+		// state (transcript / rollout / message file), never a herdr pane id.
+		var usage herdr.Usage
+		var err error
+		switch p.Harness {
+		case "codex":
+			usage, err = herdr.CodexUsage(p.TranscriptPath)
+		case "opencode":
+			usage, err = herdr.OpenCodeUsage(p.TranscriptPath)
+		case "", "claude":
+			usage, err = herdr.ClaudeUsage(p.TranscriptPath)
+		default:
+			http.Error(w, "unknown harness: "+p.Harness, http.StatusBadRequest)
+			return
+		}
 		if err != nil {
 			http.Error(w, "reading transcript: "+err.Error(), http.StatusBadRequest)
 			return