Bound native input diagnostics and pending-host teardown

[wieslawsoltes]

Problem and resulting behavior

Native clipboard requests may still own V8 persistent resolver and file handles when a window closes. Releasing those members after isolate disposal can crash the native worker. At the same time, reproducing an input crash requires symbols for the exact packaged macOS runtime and a bounded stress path that covers pointer/focus state and legacy clipboard completion.

This layer clears pending host-promise and file targets while the isolate lock is still held, before the context and isolate are disposed. It also emits a dSYM from the exact macOS Release runtime and strips the shipped binary afterward, so diagnostics add no normal-path runtime or installed-package cost.

Dependency and issue mapping

• Stacks on the typed desktop capability ABI prerequisite for Add a bounded async Clipboard API host ABI for native runtimes #86/Complete host-driven native close veto lifecycle #87 at exact commit 4b61f2102c6aa987045d5d3ddd4b0ceb973bf909.
• Implements the teardown regression tracked by Diagnose native worker crash during legacy clipboard completion #89 and retains the bounded diagnostics needed to investigate input/focus failures.
• Exact cumulative head: 537d2fb9c0ab7553ec27b028dc236dd893b53f4f.
• Six changed files; no unrelated desktop capability, Worker, or consolidation changes.

Scope and bounds

• Release-only macOS line tables are externalized with dsymutil; the packaged native runtime is stripped after symbol extraction.
• The exact symbol artifact uses compression level 9 and three-day retention.
• A focused input-diagnostics-pointer-focus native filter covers 10,000 focus transitions, 10,000 trusted Meta-C clipboard inputs/completions, and destruction with a pending host promise.
• Clipboard stress drains in batches of 16 and fails if 10,000 completions take 15 seconds or more.
• The shutdown regression leaves the host request pending intentionally, then destroys the engine to exercise the isolate-lifetime boundary.

Validation

• Cumulative Release V8 native engine build succeeds.
• Focused native filter: 5/5 passes.
• 10,000 focus transitions: 0.15-0.19 ms.
• 10,000 clipboard completions: 1.60-1.61 s; pending high-water 16.
• Release compatibility architecture tests: 7/7.
• Native workflow policy tests: 6/6.
• Native binary ABI tests: 2/2.
• Shell syntax and git diff --check pass.

Stack

This is the cumulative top of the native desktop capability stack. Only its changed-behavior native document and precompiled/V8 gates qualify the atomic stack merge. Draft consolidation PR #76 remains open and unmerged.