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/math_checks.json

@@ -0,0 +1,14 @@
+{
+  "experiment_type": "analytic_sample_size_and_synthetic_sanity_only",
+  "python": "3.12.14",
+  "numpy": "2.3.5",
+  "scipy": "1.17.0",
+  "n_zero_error_any": 758,
+  "n_zero_error_count_tail_sum": 75321,
+  "n_zero_error_any_fixed_sequence": 299,
+  "n_zero_error_count_fixed_sequence": 19172,
+  "any_upper_n80": 0.09075042258738893,
+  "any_upper_n1000": 0.007581963587247506,
+  "detector_training": "not run",
+  "real_dataset_metrics": "not measured"
+}