add blog post with graphs (heatmap, timeline, asymmetry)

add transfer affinity matrix to README

add chemical NER target findings from apr8-chem-target branch

update README with asymmetric transfer findings from chemical NER experiments

add YAML metadata and results summary to model card

add experiment results, findings, and analysis (93 experiments)

experiment 90: revert to cosine scheduler (mean 0.8535 > constant_with_warmup mean 0.8488 over multiple runs)

experiment 45: constant_with_warmup scheduler (f1=0.8629, new best!)

experiment 15: chem 25% jnlpba 15% disease 60% (f1=0.8605, new best)

experiment 13: chem 30% jnlpba 20% disease 50%, batch=64 (f1=0.8543)

experiment 9: 3-stage chem->jnlpba->disease, batch=64 (f1=0.8519, +0.005)

experiment 2: bc5cdr_chem 50/50 pretrain (f1=0.8470, +0.044 over baseline)

experiment 0: baseline ncbi_disease only (f1=0.8033)

initial commit