Add SFSymbols direct linking support via DarwinPrivateFrameworks

[Kyle-Ye]

Summary

• Add LINK_SFSYMBOLS build flag and OPENSWIFTUI_LINK_SFSYMBOLS Swift define following the CoreUI pattern
• Bump DarwinPrivateFrameworks dependency to include the new SFSymbols product
• Replace dlopen/dlsym shim with direct import SFSymbols when the flag is enabled, keeping the dlopen fallback for non-linking builds

Test plan

• Verify swift build succeeds with OPENSWIFTUI_USE_LOCAL_DEPS=1
• Verify SFSymbolsShimsTests pass on Darwin
• Verify non-Darwin / SPI builds still compile (dlopen fallback)

[augmentcode]

🤖 Augment PR Summary

Summary: Adds optional direct linking to the private SFSymbols framework via DarwinPrivateFrameworks.

Build: Introduces LINK_SFSYMBOLS env flag and OPENSWIFTUI_LINK_SFSYMBOLS Swift define, mirroring the CoreUI pattern.

Deps: Updates Package.resolved to a newer DarwinPrivateFrameworks revision that includes an SFSymbols product.

SwiftPM: Wires the SFSymbols product into OpenSwiftUICore when linking is enabled.

Runtime: Uses direct import SFSymbols under the flag, otherwise keeps the dlopen/dlsym shim for non-link builds.

Goal: Enable direct symbol access while preserving portability/fallback behavior.

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[augmentcode]

Review completed. 2 suggestions posted.

Comment augment review to trigger a new review at any time.

[augmentcode]

When OPENSWIFTUI_LINK_SFSYMBOLS is enabled this file no longer defines the SFSymbols shim type, but other files/tests reference SFSymbols.* without importing the SFSymbols module (e.g. Sources/OpenSwiftUICore/View/Image/NamedImage.swift, Tests/OpenSwiftUICoreTests/Util/SFSymbolsShimsTests.swift). That will likely become an unresolved identifier compile error in linking builds.

Severity: high

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[augmentcode]

In the remote-deps branch, adding DarwinPrivateFrameworks is gated by attributeGraphCondition || renderBoxCondition || linkCoreUI || linkSFSymbols, but not linkBacklightServices (unlike the local-deps branch). This can break builds when LINK_COREUI=0 but LINK_BACKLIGHTSERVICES=1 by omitting the required package dependency.

Severity: medium

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 13.99%. Comparing base (7425dc9) to head (4ec0a05).
⚠️ Report is 1 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (7425dc9) and HEAD (4ec0a05). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (7425dc9)	HEAD (4ec0a05)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #810       +/-   ##
===========================================
- Coverage   27.41%   13.99%   -13.43%     
===========================================
  Files         660      624       -36     
  Lines       42376    37809     -4567     
===========================================
- Hits        11619     5290     -6329     
- Misses      30757    32519     +1762     

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