Implement resolvable text segment attributes

[Kyle-Ye]

Summary

• Implement resolvable text segment construction, restoration, toggling, updates, and serialization.
• Add platform attribute resolution and dynamic text update-schedule aggregation.
• Add focused coverage for segment behavior, size variants, attribute conflicts, update ordering, and reduced timeline schedules.

[tuist]

🛠️ Tuist Run Report 🛠️

Tests 🧪

Scheme	Status	Cache hit rate	Tests	Skipped	Ran	Commit
OpenSwiftUI	✅	0 %	1089	0	1089	f667b34d2

Builds 🔨

Scheme	Status	Duration	Commit
OpenSwiftUI	✅	2m 43s	f667b34d2

[codecov]

Codecov Report

❌ Patch coverage is 93.82353% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 28.80%. Comparing base (8adfd64) to head (1017949).

Files with missing lines	Patch %	Lines
.../Text/Resolve/ResolvableTextSegmentAttribute.swift	94.44%	16 Missing ⚠️
.../ConfigurationBasedResolvableStringAttribute.swift	0.00%	4 Missing ⚠️
...ICore/View/Text/Util/ReducedTimelineSchedule.swift	97.91%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1028      +/-   ##
==========================================
+ Coverage   27.67%   28.80%   +1.13%     
==========================================
  Files         771      771              
  Lines       60962    61288     +326     
==========================================
+ Hits        16870    17655     +785     
+ Misses      44092    43633     -459     

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