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/README.md

@@ -0,0 +1,7 @@
+# Actual results only
+
+- `unit_tests.txt`: executed CPU tests and explicitly skipped PyTorch tests.
+- `math_checks.json`: analytic calibration sample-size calculations.
+- `environment.json`: observed runtime availability.
+
+No trained detector scores, dataset performance, latency or VRAM numbers exist. Tests use synthetic fixtures. No table cell marked pending should be interpreted as zero performance.