fix(thumbnail): [PKG-TOOL-THUMB-04] protect event names and nested once dispatch

refactor/changes/2026-09-13-PKG-TOOL-THUMB-04-emitter.md

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+# PKG-TOOL-THUMB-04 emitter behavior checkpoint
+
+Starts from 3bff236145805ecae46ce60ff5c5710189560755. This closes reproduced event
+registry defects independently of the pending 3.5.31/4.4.0 default-policy choice.
+04 remains doing; no default options, extraction timing or public types change.
+
+## Before and after
+
+The inherited tiny-emitter structure treats Object.prototype members as event
+arrays. emit/on/off can fail on names such as __proto__, constructor and toString;
+inherited getters/setters can intercept a replaced public e registry. Nested emits
+take separate snapshots, allowing one once wrapper to run in an inner dispatch
+and then again when the outer snapshot resumes, even after the inner throw was
+caught. Re-registering its original callback does not make that duplicate correct.
+
+The candidate checks own keys and creates new entries with data descriptors,
+retaining the registry object/prototype and ordinary descriptor flags. Each once
+closure is consumed before removal/callback invocation. Normal listener order,
+snapshot behavior, callback ctx, symbols/numbers, duplicate independent
+registrations, original-function removal and synchronous exception identity remain.
+The design matches the already-tested core approach, without adding a runtime
+dependency on the core or erasing this tool's declaration-specific tuple boundary.
+
+Six new Node cases pass 1/fail 5 on the frozen workspace. Candidate source and
+artifacts repeat them together with the unchanged input/extraction/facade tests.
+The new real-browser case verifies special names, nested once and native DOM
+cleanup. Existing extraction, native media controls and Monaco cases are rerun
+for source/main/legacy because the runtime bundle has changed. Windows WebKit
+Blob failures remain explicit unavailable controls, not successful extraction.
+Installed package checks repeat after the final package documentation/build.
+
+The upstream attribution remains in every bundle and pack. The provenance ledger
+records these intentional local fixes separately from the previous type-only
+adaptation. THUMB-EVENT-01 tracks closure evidence; default-policy, historical CSS
+and actual supported Safari/core integration gates are unaffected.
+
+Revert this checkpoint to roll back only the emitter fixes and their records;
+run the normal package build and installed checks again. Keep earlier lifecycle,
+public declaration and distribution fixes. No push, tag or publication.