Add FIM-Midtraining (function-aware FIM mid-training for coding agent foundation models)

[reacher-z]

Adds FIM-Midtraining to ### 3.3 Code Agents, next to the existing mid-training entries (daVinci-Dev, HE-SNR).

Function-Aware Fill-in-the-Middle as Mid-Training (arXiv:2607.12463, TMLR-line work) treats a coding agent's act→observe→continue loop as isomorphic to a function call site: mask PDG-selected functions, mid-train on rationale-first recovery, then run standard agentic post-training unchanged. Ships FIM-{7,8,14}B checkpoints + a 400K / 2.6B-token corpus; improves SWE-Bench-Verified/Lite across Qwen2.5-Coder and Qwen3 bases.

• Paper: https://arxiv.org/abs/2607.12463
• Code: https://github.com/TIGER-AI-Lab/FIM-Midtraining
• Models + data: https://huggingface.co/collections/TIGER-Lab/fim-midtraining

Numbered per the section's format. Disclosure: I'm a co-author. Thanks for maintaining this list!