fix: migrate to module.registerHooks() and fix CommonJS interop regressions

[cjnoname]

Summary

module.register() has been runtime-deprecated as DEP0205 since Node.js v25.9.0 (see nodejs/node#62401), emitting a warning on every invocation:

(node:…) [DEP0205] DeprecationWarning: `module.register()` is deprecated. Use `module.registerHooks()` instead.

This migrates register.mjs to the synchronous, in-thread module.registerHooks() (Node.js ≥ 23.5.0 / 22.15.0) when available, falling back to module.register() on older runtimes. It supersedes #585, which was closed because switching to registerHooks surfaced CommonJS interop regressions that the asynchronous worker-thread loader had hidden. This PR fixes the root causes so behaviour is unchanged — and ends up faster than the previous worker-thread loader.

Correctness: CommonJS interop under the synchronous loader

The synchronous loader routes CommonJS require() and named-export detection through the customization hooks (the old loader ran them on a worker thread and Node handled CJS itself). That exposed four issues, each fixed in hooks.mjs / src/lib.rs:

1. CommonJS named exports / transitive re-exports — import { foo } from "cjs-pkg" failed with "does not provide an export named 'foo'" for packages using __export(require("./src")). Fixed by deferring modules oxc-node does not transform (plain .js/.cjs/.json, native addons, …) and anything Node classifies as commonjs back to Node.js, so its built-in CJS named-export detection keeps working.
2. require() of TypeScript files — extensionless require("./foo") of a .ts failed because the resolve hook's nextResolve does not consult Module._extensions (where pirates installs its handler). Fixed by completing the extension via oxc-node's own resolver (resolveCjsSpecifier, honouring tsconfig paths / exports / conditions / symlinks) so the CJS loader + pirates can transpile it.
3. Source maps for CommonJS .cts — stack traces pointed at the wrong location because CJS sources were transpiled to ESM output. Fixed by deferring commonjs-format loads to Node.js (and thus pirates), which emits CJS output with an accurate inline source map.
4. Missing field 'importAttributes' — the CJS require() path does not always provide conditions/importAttributes. Fixed by making those fields optional in ResolveContext/LoadContext.

Two further robustness fixes:

• The loader-thread keep-alive MessageChannel lives only in the register() worker entry (esm.mjs), not in the shared hooks, so it no longer pins unrelated worker threads (e.g. test runners) and prevents process exit under registerHooks.
• The register() fallback uses the plain resolver directly. The synchronous-loader fast paths rely on a synchronous nextResolve; under the async worker loader nextResolve is asynchronous (so the guarding try/catch cannot catch its rejection), and the worker loader does not have the CJS interop limitations the fast paths work around.

Performance

Migrating to the in-thread synchronous loader removes the per-module worker-thread IPC of module.register(). On top of that, three optimizations were applied to the hot resolve/load path:

• Skip URL allocation — the per-resolve/per-load transformability check uses a substring regex on the raw string instead of new URL(url).pathname (~9.6× faster on that check; extension characters are never percent-encoded so it is safe), and the cheap format === "commonjs" branch is tested first in the load hook.
• Skip the speculative nextResolve for specifiers that already carry a transformable extension (e.g. ./foo.ts) — these are unconditionally oxc-node's to resolve, so relative TypeScript imports are resolved once instead of twice.
• Return resolved output directly for modules oxc-node has fully resolved outside node_modules (URL + format already known), instead of calling nextResolve with the resolved URL — which made Node redundantly re-read package.json and stat the file.

Benchmark — importing a 500-module TypeScript graph, median of 15 runs, Node v26.3.0:

loader	time
this PR (registerHooks + optimizations)	59.8 ms
current (register worker thread)	112.5 ms (1.9× slower)
tsx	196.9 ms (3.3× slower)

Verification

Rebuilt binding; integrate-module (21/21), integrate-module-bundler (22/22) and integrate-ava (9/9) all pass on Node.js 24 and 26, via both the registerHooks path and the forced register() fallback. No DEP0205 warning; cargo clippy and oxlint clean.

[cjnoname]

@Boshen Please review this PR. Thanks.