MacOS 26 Screensaver fixes

[CharlieFenton]

This PR updates 2 aspects of BOINC screensaver logic for MacOS 25:

• The BOINC screensaver coordinator runs properly under the legacy screensaver engine
• MacOS 14 and MacOS 15 broke the ability select a screensaver programmatically, so the BOINC installer cold no longer offer the option to set BOINC as your screensaver. MacOS 26 restores that capability, but using a different API. Changes in this PR implement that capability, again offering the user the option to set BOINC as their screensaver.

This code is backward compatible with earlier versions of MacOS, so it can be merged into all new releases of BOINC.

[CharlieFenton]

This is ready to merge when CI checks complete successfully

[AenBleidd]

@CharlieFenton, please fix this error:

D:\a\boinc\boinc\clientscr\screensaver.cpp(568,5): error C2065: 'graphicsAppStartTime': undeclared identifier [D:\a\boinc\boinc\win_build\boinc_os_ss.vcxproj]
D:\a\boinc\boinc\clientscr\screensaver.cpp(643,17): error C2065: 'ss_shmem': undeclared identifier [D:\a\boinc\boinc\win_build\boinc_os_ss.vcxproj]
D:\a\boinc\boinc\clientscr\screensaver.cpp(644,17): error C2065: 'ss_shmem': undeclared identifier [D:\a\boinc\boinc\win_build\boinc_os_ss.vcxproj]
D:\a\boinc\boinc\clientscr\screensaver.cpp(645,17): error C2065: 'ss_shmem': undeclared identifier [D:\a\boinc\boinc\win_build\boinc_os_ss.vcxproj]
D:\a\boinc\boinc\clientscr\screensaver.cpp(646,17): error C2065: 'ss_shmem': undeclared identifier [D:\a\boinc\boinc\win_build\boinc_os_ss.vcxproj]
D:\a\boinc\boinc\clientscr\screensaver.cpp(647,17): error C2065: 'ss_shmem': undeclared identifier [D:\a\boinc\boinc\win_build\boinc_os_ss.vcxproj]

[Copilot]

Pull Request Overview

This PR implements macOS 26 screensaver functionality fixes for BOINC, addressing two key issues: proper operation of the BOINC screensaver coordinator under the legacy screensaver engine, and restoration of programmatic screensaver selection capability that was broken in macOS 14-15.

Key changes include:

• Enhanced BOINC_Finish_Install utility with macOS 26 screensaver setting capabilities and improved localization support
• Restructured installer architecture to place BOINC_Finish_Install in the BOINC Data folder instead of user directories
• Improved screensaver engine stability and lifecycle management with better signal handling and resource cleanup

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
mac_installer/release_brand.sh	Updates build script to include AddRemoveUser executable and restructures BOINC_Finish_Install placement
mac_installer/release_boinc.sh	Mirrors branding script changes and removes obsolete embedded finish install handling
mac_installer/finish_install.cpp	Adds macOS 26 screensaver setting functionality, localization support, and improved argument parsing
mac_installer/PostInstall.cpp	Removes legacy screensaver setting code and updates to use centralized finish install location
mac_build/boinc.xcodeproj/*	Updates Xcode project configuration for new build dependencies and finish install handling
clientscr/.cpp/.m	Improves screensaver engine stability with better lifecycle management and signal handling
clientgui/mac/templates/*.plist	Updates plist templates with corrected DTD references and icon specifications
client/*.cpp	Minor logging improvements and security check updates for branded installations

Comments suppressed due to low confidence (1)

clientscr/Mac_Saver_ModuleView.m:147

• The comment 'CAF' is unclear and should be expanded to explain what it stands for or its purpose in this context.

bool gIsBigSur = false;

[AenBleidd]

@CharlieFenton, is it ready to be merged?

[CharlieFenton]

@AenBleidd Not quite yet. I want to investigate Copilot's latest comments first

[CharlieFenton]

@AenBleidd This should be ready to merge now.