[AZ-171] Add TensorRT tests, AC coverage gate in implement skill, optimize test infrastructure

- Add TensorRT export tests with graceful skip when no GPU available
- Add AC test coverage verification step (Step 8) to implement skill
- Add test coverage gap analysis to new-task skill
- Move exported_models fixture to conftest.py as session-scoped (shared across modules)
- Reorder tests: e2e training runs first so images/labels are available for all tests
- Consolidate teardown into single session-level cleanup in conftest.py
- Fix infrastructure tests to count files dynamically instead of hardcoded 20

Made-with: Cursor

_docs/03_implementation/batch_03_report.md

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+# Batch Report
+
+**Batch**: 3
+**Tasks**: AZ-171_dynamic_batch_export
+**Date**: 2026-03-28
+
+## Task Results
+
+| Task | Status | Files Modified | Tests | Issues |
+|------|--------|---------------|-------|--------|
+| AZ-171_dynamic_batch_export | Done | 2 files (src/exports.py, _docs/02_document/architecture.md) | 48 passed, 14 skipped, 6 errors (pre-existing) | None |
+
+## Code Review Verdict: PASS
+## Auto-Fix Attempts: 0
+## Stuck Agents: None
+
+## Next Batch: All tasks complete

_docs/03_implementation/implementation_report_dynamic_batch.md

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+# Implementation Report — Dynamic Batch Export
+
+**Date**: 2026-03-28
+**Epic**: AZ-164 (Code Improvements)
+**Total Tasks**: 1
+**Total Batches**: 1
+**Commit**: 433e080
+
+## Summary
+
+Enabled dynamic batch size for all three model export formats (ONNX, TensorRT, CoreML) by adding `dynamic=True` to the ultralytics export calls. TensorRT max batch size set to 8.
+
+## Tasks Implemented
+
+| Task | Name | Complexity | Status |
+|------|------|-----------|--------|
+| AZ-171 | dynamic_batch_export | 2 | Done |
+
+## Changes
+
+| File | Change |
+|------|--------|
+| src/exports.py | Added `dynamic=True` to export_onnx, export_tensorrt, export_coreml; changed TensorRT batch from 4 to 8 |
+| _docs/02_document/architecture.md | Updated Model Artifacts table to reflect dynamic batch support |
+
+## Test Results
+
+- 48 passed, 14 skipped, 6 errors (pre-existing ModuleNotFoundError for onnx package in e2e tests — environment dependency, not introduced by this change)