Keep the launch dump out of the session's git status

The .orchestra directory showed up as untracked work in the very worktree whose
own launch context said "uncommitted changes: false". It would have polluted
the quality gate, the review diff, and the agent's reading of git status. A
.gitignore of "*" inside the directory ignores it including itself. The
worker's done marker lives there too and had the same problem.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/herdr/tmux_test.go

@@ -3,6 +3,7 @@ package herdr
 import (
 	"context"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -98,3 +99,29 @@ func TestTmuxSessionNameKeepsCollisionResistantSuffix(t *testing.T) {
 		t.Fatalf("unsafe tmux session names %q %q", a, b)
 	}
 }
+
+// The launch dump is Orchestra's scratch space, not the session's work. A
+// worktree that starts dirty pollutes the gate, the review diff, and the
+// agent's own reading of `git status`.
+func TestWriteLaunchContextLeavesTheWorktreeClean(t *testing.T) {
+	dir := t.TempDir()
+	for _, args := range [][]string{{"init"}, {"config", "user.email", "t@t"}, {"config", "user.name", "t"}, {"commit", "--allow-empty", "-m", "init"}} {
+		if out, err := exec.Command("git", append([]string{"-C", dir}, args...)...).CombinedOutput(); err != nil {
+			t.Fatalf("git %v: %v: %s", args, err, out)
+		}
+	}
+	if err := WriteLaunchContext(dir, "the instruction"); err != nil {
+		t.Fatal(err)
+	}
+	b, err := os.ReadFile(filepath.Join(dir, LaunchContextFile))
+	if err != nil || string(b) != "the instruction" {
+		t.Fatalf("launch context = %q, err %v", b, err)
+	}
+	out, err := exec.Command("git", "-C", dir, "status", "--short").CombinedOutput()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if strings.TrimSpace(string(out)) != "" {
+		t.Fatalf("worktree is dirty after a launch dump:\n%s", out)
+	}
+}