Release pending host handles before V8 teardown

[wieslawsoltes]

Problem

Destroying an engine with an unfinished clipboard/file host request disposed V8 before persistent contexts and promise resolvers were released. The public-ABI reproducer and packaged Code OSS crash shared all eight WebScene frames and exited 139 before the fix.

Change

Clear host_promise_targets and file_targets under the isolate lock before context/isolate disposal. Add the direct pending-request teardown regression while preserving the 10,000 completed-copy stress and symbolized package diagnostics.

Validation

• Focused comparison: 1 commit, behind 0.
• The pre-fix public-ABI reproducer exits 139; replacing only the dylib with the candidate prints clean destroy and exits 0.
• macOS package producer, direct teardown regression, 10,000-operation stress, hosted three-platform CI, NativeAOT, all runtime packages/consumers, cross-RID evidence, and release verification passed.
• Rebuilt Code OSS/AppScene passed real-editor smoke and normal close without the worker SIGSEGV.

Integration

Closes #89.

Equivalent commit 31e3d8ad is already in draft consolidation PR #76. This PR targets the exact diagnostic commit immediately before the runtime fix for isolated review. Keep it open and do not merge it to main.

[wieslawsoltes]

Closing this older isolated review as superseded by merged native Stack #186. The pending-host-handle teardown fix and its direct regression are included in focused PRs #184/#185 on current main, atomically merged at 75b826d0496b288a11eed54510ebdc45f5b52c1b; issue #89 is closed. No implementation is being discarded.