refactor: 将子模块转为普通目录，移除外部 git 依赖

- 移除 JEPA/lejepa-identifiability 子模块 gitlink
- 移除 research/multiply/MultiPLY 子模块 gitlink
- 删除 .gitmodules（不再有外部 URL 依赖）
- 两个目录内容作为普通文件纳入主仓库追踪
- 删除各自内部 .git 目录，消除嵌套 git 仓库

JEPA/lejepa-identifiability/experiments/configs/grid.yaml

@@ -0,0 +1,27 @@
+# Grid search over lambda and rho (bound verification figure)
+# python run.py --config configs/grid.yaml --lamb 0.01 --rho 0.9 --seed 0
+
+experiment: grid
+out: results/grid
+
+# Data
+N: 2
+source_dist: gaussian
+num_eval: 10000
+
+# Training (shared)
+steps: 20000
+lr: 3.0e-3
+batch_size: 256
+log_every: 500
+
+# Encoder
+encoder: mlp
+hidden: 256
+mixing: spiral
+mode: lejepa
+
+# Sweep dimensions
+lambs: [1.0e-6, 1.0e-5, 1.0e-4, 1.0e-3, 5.0e-3, 1.0e-2, 5.0e-2, 1.0e-1, 5.0e-1]
+rhos: [0.3, 0.5, 0.7, 0.8, 0.9, 0.95, 0.99]
+seeds: [0, 1, 2]