feat(jev): System One routing — single-pass Jev decision engine (model=jev-auto)

Implements the open Jev interface pattern (TypeSafe System One) as a
local decision engine distilled from our own System 2 heuristic router:

- src/routing/jev/types.ts       — choice/score/noul question contract
- src/routing/jev/optionAttention.ts — hashed-trigram option-attention
  engine (pure TS, zero deps, dynamic option sets, query cache)
- src/routing/jev/jevRouter.ts   — RouteDecision-compatible head with
  confidence guard → System 2 fallback below p<0.22
- src/routing/jev/remote.ts      — Jev-compatible endpoint client
  (ekzhang/openjev-sglang / api.typesafe.ai via A3M_JEV_URL)
- tools/distill.mjs              — System2→System1 corpus generator
- tools/train_jev.py             — vectorized numpy trainer (CE+MSE+CE)
- tools/calibrate_temp.py        — binary-search temperature calibration
- weights: 97.8% train top-1, mean top-prob 0.90 calibrated, 1.1MB
- modelMapper: model="jev-auto" → jevRoute
- warm latency ~2ms/decision (32 options), 100 opts < 150ms guard
- tests: 10 new (engine contract, dynamic options, determinism,
  fallback, perf); full suite 188/188

Sources: harshatheg/Qwen-2.5-1B-RLCD, TheoLeeCJ/SemIf (ex-OpenJev),
vinnylarouge/jevlike, ekzhang/openjev-sglang

Author: Das-rebel