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

configs/ablations.csv

@@ -0,0 +1,18 @@
+id,segmentation_loss,gate,area_weight,calibration,status
+B00,bce,none,no,tail_sum_CP,prepared
+B01,dice,none,no,tail_sum_CP,prepared
+B02,bce_dice,none,no,tail_sum_CP,prepared
+B03,focal,none,no,tail_sum_CP,prepared
+B04,iou,none,no,tail_sum_CP,prepared
+B05,bce_dice,bce,no,tail_sum_CP,prepared
+B06,bce_dice,constrained,yes,tail_sum_CP,prepared
+B07,bce_dice,constrained,no,tail_sum_CP,prepared
+B08,SLS,none,no,tail_sum_CP,upstream_audit_required
+B09,SD,none,no,tail_sum_CP,upstream_audit_required
+B10,AC-SLSIoU,none,no,tail_sum_CP,upstream_audit_required
+B11,bce_dice,fixed_penalty,yes,tail_sum_CP,not_implemented
+B12,bce_dice,constrained,yes,empirical_only,not_implemented
+B13,bce_dice,graph_gate,yes,tail_sum_CP,not_implemented
+B14,bce_dice,none,no,fixed_sequence,prepared
+B15,bce_dice,bce,no,fixed_sequence,prepared
+B16,bce_dice,constrained,yes,fixed_sequence,prepared