Single-source the version from package.json (closes #5)

src/index.ts imports package.json for VERSION and bin/quak.ts passes
VERSION to commander, so package.json is the only place the version is
written. tsc copies package.json to dist/package.json, so the import
resolves from the built output; script/build runs the built CLI with
--version to prove it. A test checks VERSION and quak --version against
package.json.

Model: opus-5-5

script/build

@@ -45,10 +45,24 @@ for (const bin of bins) {
 '
 }
 
+# src/index.ts imports ../package.json for the version, which tsc copies to
+# dist/package.json. Running the built CLI proves that import resolves from
+# dist/ and reports the version package.json declares.
+verify_version() {
+    built="$(node dist/bin/quak.js --version)"
+    declared="$(node -p 'require("./package.json").version')"
+    if [ "$built" != "$declared" ]; then
+        echo "build: dist/bin/quak.js reports $built, package.json declares $declared" >&2
+        exit 1
+    fi
+    echo "build: dist/bin/quak.js reports version $built"
+}
+
 main() {
     cd "$ROOT"
     yarn run tsc
     verify_entrypoints
+    verify_version
 }
 
 main "$@"