Simplify README and document SFT SAE checkpoints

Add consolidated SFT and PPO SAE checkpoint metrics

Add SFT-chain SAEs (7 stages x 4 layers, k=64, warm-start chain instruct_base->sft_step348)

explain what each chain tests and the three-chain design logic

explain what each chain tests and the three-chain design logic

Remove layer23/ — superseded by sae_flexible/

Remove layer18/ — superseded by sae_flexible/

Remove layer12/ — superseded by sae_flexible/

Remove layer6/ — superseded by sae_flexible/

Remove 32 stray root-level .pt files (duplicates of sae_flexible/)

add flexible chain at canonical path (mirrors layer*/ folders during migration)

add kl=0.025 sweep chain

add strict L23 k=256 retrain

add strict chain k=64 SAEs

README: mixed K (64 for L6/12/18, 256 for L23); refresh quality table

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README: NMSE + frac_rec from honest-val eval

Replace stale Apr 23 plots with sae_eval.csv (honest val)

SAE chain v2: 20-epoch retrain on 80/20 val split (seed=0)

Update README.md

README v2: warm-start rerun, full hyperparams, YAML metadata

README: warm-start retrain, drift metric fix, ablation in progress

warm-start SAEs v2: 8 stages x 4 layers, L23 FVE 0.71 to 0.85, loss recovered >0.93 all layers

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initial commit