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.

docs/rfc/implemented/feature/2026-07-05-dynamic-workflows.md

@@ -26,7 +26,7 @@ One deliberate strictness DIVERGENCE from CC: hook misuse — unknown or deferre
 
 **Why node:worker_threads**: one run uses one unpooled worker because a workflow run is already heavyweight relative to thread startup. The script runs in a vm context inside the worker, keeping the script-visible surface to the hook contract instead of exposing a bare worker realm, while `agent()` bridges by message-port RPC to I/O-bound child loops on the host. This keeps `start()` from blocking the host on the script's synchronous slice, makes the post-cancel deadline end in a real `worker.terminate()`, and gives cross-thread values a serialization boundary by construction. isolated-vm was rejected for its maintenance state, required `--no-node-snapshot` consumer flag on Node ≥ 20, and node-gyp fallback.
 
-Host-side meta validation and body pre-parsing preserve the seam's synchronous errors, and private enum-keyed payload maps define the wire protocol. Pending async starts, published child records, one host cancellation signal, worker-death reaping, result precedence, and disposal quiescence preserve the subagent run contract across that wire; the [agent-scope runtime-design RFC](../architecture/2026-07-12-agent-scope-runtime-design.md#workflow-children-are-pending-starts-or-published-records) owns those race algorithms. Coverage uses an in-process `MessageChannel` for worker-side logic that main-process V8 coverage cannot see and separately proves the built `lib/worker.js`—a second tsdown entry sanctioned by the `"./worker"` subpath export—under plain Node in the built-bin smoke gate.
+Host-side meta validation and body pre-parsing preserve the seam's synchronous errors, and private enum-keyed payload maps define the wire protocol. Pending async starts, published child records, one host cancellation signal, worker-death reaping, result precedence, and disposal quiescence preserve the subagent run contract across that wire; the [agent-scope runtime-design RFC](../architecture/2026-07-12-agent-scope-runtime-design.md#workflow-children-are-pending-starts-or-published-records) owns those race algorithms. Coverage uses an in-process `MessageChannel` for worker-side logic that main-process V8 coverage cannot see and separately proves the built `lib/worker.cjs`—a second tsdown entry sanctioned by the `"./worker"` subpath export—under plain Node in the built-bin smoke gate.
 
 **Meta as data, never evaluated**: the meta block reaches the seam as a plain JSON request field (the tool's schema-validated `meta` parameter) and the engine only shape-validates it, every violation named. This is a host-isolation invariant, not a convenience: evaluating a meta literal host-side — even one contractually "pure", in an empty timed vm context — hands script-controlled getters a host stack with no timeout the moment the result is READ, defeating the exact spin isolation the worker thread buys.