ci(version): add version sync check between package.json and Cargo.toml (#277)

Add automated verification that package.json and cli/Cargo.toml versions
stay in sync. This prevents version drift between the npm package and
Rust CLI binary.

- Add CI job to check version sync on push/PR
- Update pre-commit hook to sync versions automatically
- Update ci:version script to include version sync step
- Add check-version-sync.js script for CI validation

scripts/check-version-sync.js

@@ -0,0 +1,39 @@
+#!/usr/bin/env node
+
+/**
+ * Verifies that package.json and cli/Cargo.toml have the same version.
+ * Used in CI to catch version drift.
+ */
+
+import { readFileSync } from 'fs';
+import { dirname, join } from 'path';
+import { fileURLToPath } from 'url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const rootDir = join(__dirname, '..');
+
+// Read package.json version
+const packageJson = JSON.parse(readFileSync(join(rootDir, 'package.json'), 'utf-8'));
+const packageVersion = packageJson.version;
+
+// Read Cargo.toml version
+const cargoToml = readFileSync(join(rootDir, 'cli/Cargo.toml'), 'utf-8');
+const cargoVersionMatch = cargoToml.match(/^version\s*=\s*"([^"]*)"/m);
+
+if (!cargoVersionMatch) {
+  console.error('Could not find version in cli/Cargo.toml');
+  process.exit(1);
+}
+
+const cargoVersion = cargoVersionMatch[1];
+
+if (packageVersion !== cargoVersion) {
+  console.error('Version mismatch detected!');
+  console.error(`  package.json:    ${packageVersion}`);
+  console.error(`  cli/Cargo.toml:  ${cargoVersion}`);
+  console.error('');
+  console.error("Run 'pnpm run version:sync' to fix this.");
+  process.exit(1);
+}
+
+console.log(`Versions are in sync: ${packageVersion}`);