fix(pkg): support worker-backed tools in single exe

pkg stores application files in a virtual filesystem, and its
worker_threads hook discovers worker entry points only when they are passed
as filesystem strings. Convert the code-runtime entry with fileURLToPath()
and return the workflow built entry as a string while retaining its
source-mode data URL bootstrap.

Emit worker entry bundles as CommonJS .cjs files. pkg executes a VFS-backed
string-path worker through Module._compile, so an ESM-only entry can be
present in the executable yet still fail when launched. Keep the public hosts
ESM, adapt worker startup accordingly, and align exports, package file lists,
workspace constraints, documentation, and built-worker tests with the actual
artifact format.

Expand the custom-config executable smoke to load the Code Mode and workflow
plugins and script real run_code and zero-agent workflow calls. Require both
tools to return 42 from workers launched inside the pkg VFS, turning worker
support from an asset-presence assumption into an end-to-end runtime
contract.

Update the implemented RFC and verification gates to describe and exercise
the supported built-worker path. This adds no tool or JSON-RPC protocol shape;
it fixes how existing worker-backed capabilities are located and executed in
the single-file distribution.

packages/code-runtime/code-runtime-worker/tests/built-lib.e2e.ts

@@ -8,7 +8,7 @@ import { describe, expect, it } from 'vitest'
  * BUILT-ARTIFACT smoke for the published package (the real-load-path guard
  * from docs/testing.md): the unit suite runs `src/` under vitest, where the
  * worker entry resolves to `src/worker.ts` — a consumer runs `lib/index.js`
- * under plain `node`, where it must resolve the sibling `lib/worker.js`
+ * under plain `node`, where it must resolve the sibling `lib/worker.cjs`
  * bundle instead. This spawns plain `node` (NOT tsx) from inside the package
  * directory and imports the package BY NAME, so resolution flows through the
  * real `exports` map exactly as it would from a downstream install; the
@@ -21,11 +21,11 @@ import { describe, expect, it } from 'vitest'
  */
 
 const pkgDir = fileURLToPath(new URL('..', import.meta.url))
-const built = ['lib/index.js', 'lib/worker.js'].every(file => existsSync(join(pkgDir, file)))
+const built = ['lib/index.js', 'lib/worker.cjs'].every(file => existsSync(join(pkgDir, file)))
   && existsSync(join(pkgDir, '../code-runtime/lib/index.js'))
 
 describe.skipIf(!built)('built lib real load path (plain node)', () => {
-  it('runs a TypeScript program with a binding through lib/index.js and its lib/worker.js entry', async () => {
+  it('runs a TypeScript program with a binding through lib/index.js and its lib/worker.cjs entry', async () => {
     const script = `
       const { Context } = await import('cordis')
       const { WorkerCodeRuntime } = await import('@deepseek-ai/dsh-code-runtime-worker')