fix(core,cli,ci): harden runtime resolution + inline constant + smoke test (#458)

Guard buildHyperframesRuntimeScript() against missing entry.ts so it
returns null instead of crashing with esbuild stderr output. Add
getHyperframeRuntimeScript() that returns the pre-built IIFE as a
baked-in string constant — no esbuild, no file I/O, no import.meta.url.

Consolidate CLI runtime source resolution into a single module with
a clear priority chain: esbuild from source (dev) → inlined constant
(production) → pre-built artifact file (fallback).

Add CI smoke test that npm-packs the CLI, installs globally, runs
hyperframes preview, and asserts no stderr errors + runtime endpoint
returns JS.

Bump version to 0.4.16.

packages/core/src/index.ts

@@ -139,6 +139,7 @@ export {
   HYPERFRAME_CONTROL_ACTIONS,
   type HyperframeControlAction,
 } from "./inline-scripts/runtimeContract";
+export { getHyperframeRuntimeScript } from "./generated/runtime-inline";
 export {
   buildHyperframesRuntimeScript,
   type HyperframesRuntimeBuildOptions,

packages/core/src/inline-scripts/hyperframe.ts

@@ -17,6 +17,6 @@ export const HYPERFRAME_RUNTIME_CONTRACT: HyperframeRuntimeContract = {
   messageSources: HYPERFRAME_BRIDGE_SOURCES,
 };
 
-export function loadHyperframeRuntimeSource(): string {
+export function loadHyperframeRuntimeSource(): string | null {
   return buildHyperframesRuntimeScript();
 }

packages/core/src/inline-scripts/hyperframesRuntime.engine.ts

@@ -1,4 +1,5 @@
 import { buildSync } from "esbuild";
+import { existsSync } from "node:fs";
 import { dirname, resolve } from "node:path";
 import { fileURLToPath } from "node:url";
 
@@ -17,10 +18,19 @@ function applyDefaultParityMode(script: string, enabled: boolean): string {
   );
 }
 
+/**
+ * Build the runtime IIFE from source via esbuild.
+ *
+ * Returns `null` when `entry.ts` does not exist at the resolved path —
+ * this happens in bundled / published contexts where only `dist/` ships.
+ * Callers must fall back to the pre-built artifact or the inlined constant.
+ */
 export function buildHyperframesRuntimeScript(
   options: HyperframesRuntimeBuildOptions = {},
-): string {
+): string | null {
   const entryPath = resolve(dirname(fileURLToPath(import.meta.url)), "../runtime/entry.ts");
+  if (!existsSync(entryPath)) return null;
+
   const result = buildSync({
     entryPoints: [entryPath],
     bundle: true,