Phase 1 of the analytics system (/goal): the framework-independent analysis
engine. Value-type models (MetricDelta, TrendResult, DaySample, WeeklyReport,
MonthlyReport, ...) and AnalyticsEngine with documented formulas (volume,
%change, consistency, trend) and honest degradation (nil/zero/tiny baseline,
new exercise, rest day, outliers via winsorize, unit-dimension compatibility,
divide-by-zero). Calendar math takes an injected Calendar (locale/firstWeekday/
timezone/DST-safe).
AnalyticsEngineTests: 35 XCTest cases. Independently verified by compiling the
engine with swiftc and running a 42-assertion harness — all pass. (Xcode test
target not runnable in this env; assertions mirror the XCTest file.)
Registered the new files via xcodegen. Logs KC-51 phase-1 progress in ISSUES.md.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
