feat(macos): implement SCKit-based capture and prefer it to AVFoundation where available

[martona]

Description

Replaces AVFoundation's AVCaptureScreenInput as the default macOS capture backend with a ScreenCaptureKit-based implementation (macOS 14+; AVFoundation remains as fallback for older systems or SCKit setup failures).

Capture runs through SCScreenshotManager polling paced to the session frame rate, rather than an SCStream.

Two reasons:

• SCStream's update detection misses or delays small screen changes (e.g. a blinking terminal cursor), producing visible latency for keystroke echo.
• Mixing SCStream frames with screenshot frames (streaming plus polling as a fallback) causes visible flicker on translucent surfaces such as toolbar materials, because the two paths composite slightly differently.

Polling a single consistent source resolves both, at capture latency measured equal to AVFoundation. Since polling goes through the zero-copy VideoToolbox path by default, there's no CPU cost to it.

Fixes

• Cursor visibility: SCKit composites the cursor differently, fixing the long-standing AVFoundation bug where a cursor hidden by an application (e.g. while typing in a text field) never reappears in the stream.
• Host processing latency reporting on macOS (first commit): capture timestamps are derived from sample buffer PTS and survive encoder pipelining via PTS-matched bookkeeping, so Moonlight's ctrl+alt+shift+S host latency stat works on macOS.

Testing

Tested on macOS 26 (Apple silicon, VM, Mac Studio and MBP): cursor reappearance, static-screen behavior, display reconfiguration, latency stat parity, extended interactive sessions at 1080p60/4K60 with hardware (VideoToolbox) and software (x264) encoders.

Screenshot

Issues Fixed or Closed

Closes #3433

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

See our AI usage policy.

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes

[martona]

The remaining QualityGate issue is not mine; it's from 4 months ago. I can certainly fix it but I would rather keep this PR on topic.

[ReenigneArcher]

Agree on the sonar issue. Could you fix the doxygen errors before I review this? https://app.readthedocs.org/projects/sunshinestream/builds/34086280/ You can expand the failed section and ctrl + F for error: to find them.

[martona]

Done. Sorry I missed them last night.

[sonarqubecloud]

Quality Gate failed

Failed conditions
1 New issue
1 New Code Smells (required ≤ 0)

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