feat: 导入 IRSTD 研究代码与文档（小目标检测）

- 新增 irstd 核心包、scripts、tests、configs
- 新增研究文档：literature_review / mathematical_analysis / novelty_matrix / experiment_plan / research_decision / research_log / manuscript_outline
- 新增 evidence、results 数据与审计产物
- 新增 pyproject.toml、requirements、.gitignore

results/environment.json

@@ -0,0 +1,10 @@
+{
+  "python": "3.12.14 (main, Aug 25 2026, 14:00:49) [Clang 22.1.3 ]",
+  "platform": "Linux-6.18.57-x86_64-with-glibc2.39",
+  "numpy": "2.3.5",
+  "scipy": "1.17.0",
+  "Pillow": "12.3.0",
+  "torch_available": false,
+  "nvidia_smi": null,
+  "real_data_acquired": false
+}