fix: dispose orphaned sibling handle when re-marshalling the same host object

[rot1024]

Problem

Marshalling the same host object into the VM more than once leaks a QuickJS handle, which aborts the debug-sync runtime on dispose() with:

Aborted(Assertion failed: list_empty(&rt->gc_obj_list), at: quickjs.c,2036,JS_FreeRuntime)

Minimal repro:

const shared = { k: 1 };
arena.expose({ get: () => shared });
arena.evalCode(`get(); get();`); // <-- second marshal leaks

One get() is fine; the second leaks. Same for get() === get().

Root cause

The first registration stores both a wrapped (proxy) handle and its unwrapped sibling in VMMap. Once the VM frees the proxy, the host-side handle goes dead and the map entry becomes stale. The lazy eviction in VMMap.get then dropped the entry via delete(key) without disposing the still-alive sibling, orphaning it.

(Tracked this down with the debug-sync runtime: a single host-fn return registers the global graph (~420 entries) which dispose cleanly; only the re-marshalled object's sibling leaked. The leak was confirmed via VMMap.set/delete tracing showing the stale entry being deleted with dispose=undefined then re-set.)

Fix

Evict the stale entry with delete(key, true) so the orphaned sibling is disposed. The dead primary is skipped by delete's own .alive guard, so this only frees the leaked sibling.

Tests

Added src/remarshalleak.test.ts — fails (runtime abort) without the fix, passes with it. Full suite: 163 passing, typecheck + lint clean.

Scope note

This fixes the handle leak (relates to the dispose-leak family in #4 / #41). It does not change reference-identity behavior across the host boundary (get() === get() is still false) — that is a separate, deeper lifetime concern; marshalByReference remains the supported path for guaranteed identity.

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	97.48%	699 / 717
🔵	Statements	93.42%	781 / 836
🔵	Functions	95.13%	176 / 185
🔵	Branches	84.62%	490 / 579

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/vmmap.ts	95.83%	83.07%	100%	100%	74, 109, 111, 233, 236

Generated in workflow #543 for commit a6efc39 by the Vitest Coverage Report Action