Fix TestMain to find module root before building bd binary

The TestMain in beads_hash_multiclone_test.go was running `go build ./cmd/bd`
from the package directory (internal/beads) instead of the module root, causing
the build to fail with "directory not found".

Now uses `go list -m -f '{{.Dir}}'` to locate the module root and sets cmd.Dir
appropriately before building.

This fixes the integration test setup that was preventing TestRoutingIntegration
from running. (bd-g9eu)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/beads/beads_hash_multiclone_test.go

@@ -32,8 +32,18 @@ func TestMain(m *testing.M) {
 	}
 	defer os.RemoveAll(tmpDir)
 
+	// Find module root directory (where go.mod lives)
+	modRootCmd := exec.Command("go", "list", "-m", "-f", "{{.Dir}}")
+	modRootOut, err := modRootCmd.Output()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to find module root: %v\n", err)
+		os.Exit(1)
+	}
+	modRoot := strings.TrimSpace(string(modRootOut))
+
 	testBDBinary = filepath.Join(tmpDir, binName)
 	cmd := exec.Command("go", "build", "-o", testBDBinary, "./cmd/bd")
+	cmd.Dir = modRoot // Build from module root where ./cmd/bd exists
 	if out, err := cmd.CombinedOutput(); err != nil {
 		fmt.Fprintf(os.Stderr, "Failed to build bd binary: %v\n%s\n", err, out)
 		os.Exit(1)