feat(spec): merchant-ledger property + login/navigation generators

Property ledgerBalanceMatchesTxns asserts displayed balance equals
sum(Given) - sum(Received) on either ledger screen. Catches the
class of bug where the server-fed CustomerModel.balance diverges
from the local-DB-fed CoreDatabaseDao sums (stale cache, partial
sync, deleted-txn handling glitch, etc.).

Generators are gated by screen state and weighted to push the run
through login -> home -> ledger quickly:
  enterPhone (100), enterOtp (100), openCustomerOrSupplier (80),
  taps (10), swipes (2).

Phone/OTP read from process.env via esbuild defines so credentials
never land in source. cmd/internal-tools/bundle-check is a quick
sanity tool to confirm the spec bundles before running uatu test.

cmd/internal-tools/bundle-check/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/priyanshujain/uatu/internal/bundler"
+)
+
+func main() {
+	repoRoot, err := os.Getwd()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "getwd: %v\n", err)
+		os.Exit(1)
+	}
+	specApiPath := filepath.Join(repoRoot, "pkg/spec-api/src/index.ts")
+
+	result, err := bundler.Bundle(bundler.Options{
+		EntryFile: "examples/specs/merchant-ledger.ts",
+		Defines: map[string]string{
+			"UATU_TEST_PHONE": "+910000000000",
+			"UATU_TEST_OTP":   "000000",
+		},
+		Aliases: map[string]string{
+			"@uatu/spec": specApiPath,
+		},
+	})
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "bundle: %v\n", err)
+		os.Exit(1)
+	}
+	fmt.Printf("bundled: %d bytes, sha256=%s\n", len(result.JavaScript), result.SHA256)
+}