chore: release v1.5.0-fork.4

[My-Denia]

Changes

• advance CloseScreen to 1.5.0-fork.4 in package and release metadata;
• document the Rust-default Windows backend and explicit legacy C++ rollback path;
• record the completed packaged-application validation and current release boundaries;
• synchronize release-specific documentation and Linux package metadata.

Why

The Rust-default Windows migration is merged and the packaged candidate has passed the release validation required for promotion. Direct-helper microphone and webcam deadline observations did not reproduce through the Electron-managed packaged application and are documented as test-contract false negatives, not product or hardware failures.

Impact

This is a release-only change. It does not modify capture, audio, webcam, editor, exporter, native runtime, backend selection, or test-harness behavior. Rust remains the default Windows native capture backend. The packaged legacy C++ helpers remain available with CLOSESCREEN_WINDOWS_CAPTURE_BACKEND=legacy.

Tests and validation

• lint, i18n validation, TypeScript typecheck, unit, browser, and E2E suites passed;
• Rust formatting, notices, and Windows-target Rust tests passed;
• the Rust-default packaged Windows application passed recording, normal stop and finalization, editor loading, native save-dialog MP4 export, GIF export, system-audio preservation, Realtek microphone, and USB webcam smoke validation;
• microphone source/export audio was audible, non-empty, and non-silent; the exported MP4 contained 694 packets of 48 kHz stereo AAC;
• webcam preview and recording succeeded; extracted frames from the 13.13-second 1920x1080 H.264 export confirmed the picture-in-picture content;
• Windows installer packaging and native/attribution payload checks passed for the local candidate.

Limitations

• packaged legacy UI behavior was not repeated in this validation round and is NOT VERIFIED here;
• Windows and Linux are the current unsigned release targets; successful Linux packaging does not by itself establish Linux runtime validation;
• macOS, Windows ARM64, multi-monitor behavior, broad external-device matrices, and GPU/driver matrices are not verified or claimed;
• Computer Use did not connect because of the automation sandbox environment; this is not a CloseScreen product failure.

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