feat: add user module registration for reusable ES modules

[simongdavies]

Add add_module/remove_module/clear_modules API to JSSandbox, allowing handlers (and other modules) to import reusable ES modules using the 'namespace:name' convention (default namespace: 'user').

Guest runtime:

• Add UserModuleLoader (Resolver + Loader) for lazy compilation
• Add register_module guest function
• Modules compiled on first import, avoiding ordering issues

Host library (hyperlight-js):

• Add modules HashMap to JSSandbox with full CRUD API
• add_module / add_module_ns / remove_module / remove_module_ns / clear_modules
• Modules registered before handlers in get_loaded_sandbox()
• Export DEFAULT_MODULE_NAMESPACE constant
• Namespace validation: 'host' reserved, no colons allowed

NAPI wrapper (js-host-api):

• Add addModule / removeModule / clearModules on JSSandboxWrapper
• Error enrichment wrapping for new sync methods

Import capabilities:

• User modules can import other user modules
• User modules can import built-in modules (crypto, console, etc.)
• User modules can import host function modules (host:X)
• Missing modules fail at getLoadedSandbox() with clear errors

[ludfjig]

Reviewed the rust code, looks good!

[Copilot]

Pull request overview

Adds first-class “user module” registration so handlers (and other modules) can import reusable ES modules via the <namespace>:<name> convention (defaulting to user:), spanning the Rust host library, the guest runtime loader, and the Node.js NAPI wrapper.

Changes:

• Implemented user-module storage/CRUD on JSSandbox and registration into the guest before handlers load.
• Added guest-side lazy module resolution/loading plus a register_module guest function.
• Added NAPI/JS wrapper APIs, docs, examples, and comprehensive Rust/JS integration tests.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/js-host-api/tests/user-modules.test.js	New vitest suite covering add/remove/clear + import/lifecycle behaviors via NAPI.
src/js-host-api/src/lib.rs	Adds NAPI boundary validation and sync add_module/remove_module/clear_modules methods.
src/js-host-api/lib.js	Wraps new sync module methods for error-code enrichment (wrapSync).
src/js-host-api/examples/user-modules.js	New Node example demonstrating module registration/imports and shared module state.
src/js-host-api/README.md	Documents user module APIs and import conventions; adds a “User Modules” section.
src/hyperlight-js/tests/user_modules.rs	New Rust integration tests for module registration/import behavior and lifecycle.
src/hyperlight-js/src/sandbox/js_sandbox.rs	Implements module storage, namespace validation, and guest registration ordering.
src/hyperlight-js/src/lib.rs	Re-exports module-related constants and validation helpers.
src/hyperlight-js/examples/user_modules/main.rs	New Rust example demonstrating user modules and shared state patterns.
src/hyperlight-js/Cargo.toml	Registers the new user_modules example target.
src/hyperlight-js-runtime/src/main/hyperlight.rs	Adds register_module guest function entrypoint.
src/hyperlight-js-runtime/src/lib.rs	Adds UserModuleLoader (resolver+loader) and runtime-side module registration storage.
README.md	Updates top-level pointer to JS Host API to mention user modules/host functions.
Justfile	Runs the new js-host-api user-modules.js example as part of example runs.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

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