feat: native Metal distillation command + .core/ai config
Add `lem distill` — full Go pipeline for self-distillation using
go-mlx (native Metal inference) and go-i18n/reversal (v3 grammar
scoring). Replaces the Python distill.py bridge entirely.
New files:
- .core/ai/ai.yaml: global defaults (scorer, generation, distill)
- .core/ai/models/gemma3/{27b,1b}.yaml: model configs with paths,
kernel, lessons, baselines
- .core/ai/probes.yaml: probe sets grouped by training phase
- pkg/lem/config.go: YAML config loaders for .core/ai/
- pkg/lem/grammar.go: in-process grammar scoring (ComputeGrammarScore,
ComputeDelta, ScoreResponse) extracted from cmd/scorer
- pkg/lem/distill.go: RunDistill command — best-of-N generation,
grammar quality gate, training JSONL output
- pkg/lem/backend_metal.go: blank import for go-mlx Metal registration
Co-Authored-By: Virgil <virgil@lethean.io>
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