AGI Clock: moved 122d further (2026-04-15)

Methodology v1.4.0. AGI projection moved later (2026-12-15 → 2027-04-16) after three changes. (1) Benchmark signals (SWE-bench, HLE, ARC-AGI-2, FrontierMath) now use sigmoid (saturating-exponential) extrapolation instead of linear. Benchmarks are bounded; linear models overstate how fast the last 10pp closes and were pulling the AGI date ~4 months too early. (2) METR task-horizon weight raised 0.35 → 0.45: it is the only direct economic-capability measure and should dominate benchmark proxies. (3) Metaculus weight raised 0.15 → 0.20 as a reserved slot; currently absent because Metaculus gates Community Prediction data to a whitelist that excludes AGI questions (access request sent to api-requests@metaculus.com on 2026-04-15). Benchmark aggregate weight dropped 0.50 → 0.35.