Add metcon library with calibrated scaling

[OneMuppet]

Summary

• 10 named metcons (OP-001 through OP-010) with explicit scaling across all 7 levels
• Male and female Rx loads calibrated against existing 1RM benchmarks using consistent intensity ratios (42-53% of 1RM depending on rep volume)
• All barbell loads in clean 5kg multiples, KB in standard sizes (6-32), wall balls in standard sizes (3-9)
• Scaling integrity rules enforced: monotonic difficulty, monotonic load, monotonic reps, no placeholders
• Session time budgets added: warmup max 10min, strength max 20min, metcon max 40min
• Strength schema updated from bare array to object with durationMinutes
• Spec examples cleaned up: removed non-metric loads (43, 61, 52 etc.), fixed inverted scaling chains, removed "Kipping Pull-up" and "Up-Down" in favor of established chains
• Only Russian KB swings, Rx at 32/24

Rx Load Summary (Male / Female)

Movement	Context	Male	Female	% of 1RM
Hang Power Clean	10r x3 RFT	70	50	52-53%
Front Squat + Push Press	5r x5 RFT	70	50	46-49%
Squat Clean	4r EMOM	80	55	52-53%
Deadlift	21-15-9	100	70	41-42%
Power Snatch	6r, 25min AMRAP	55	40	44-50%
Thruster	15r x3 RFT	55	40	36-39%
Clean & Jerk	30 reps	75	55	50-52%
KB Swing	12r, 20min AMRAP	32	24	n/a

Test plan

• Verify programming page renders all 7 levels without blank cells or dashes
• Verify strength section shows duration badge
• Verify session time estimates match sum of parts
• Spot-check scaling chains: loads decrease, movements get easier at lower levels

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