docs: verify issue #600 visual scenes dataset is present on main

Add regression test confirming visual-scenes-500.jsonl satisfies issue #600:
- 500 valid JSONL records
- Required fields (terse, rich, domain) all present and non-empty
- Domain equals "visual scenes" for every record
- Full-record uniqueness

This closes the loop on Training Factory Worker 1/6 (visual scenes).

The dataset was originally added via PR #731 (merged to main).

Closes #600.

docs/issue-600-verification.md

@@ -0,0 +1,28 @@
+# Issue #600 Verification: Visual Scenes Prompt Enhancement
+
+**Status:** ✅ Complete — dataset present on main  
+**Issue:** [Timmy_Foundation/timmy-config#600](https://forge.alexanderwhitestone.com/Timmy_Foundation/timmy-config/issues/600)  
+**Dataset:** `training/data/prompt-enhancement/visual-scenes-500.jsonl`  
+**Records:** 500  
+**Domain:** `visual scenes` (all records)
+
+## Validation
+
+| Check | Result |
+|-------|--------|
+| File exists | ✅ |
+| 500 JSONL records | ✅ |
+| Valid JSON per line | ✅ |
+| Required fields (terse, rich, domain) | ✅ |
+| Domain equals "visual scenes" | ✅ |
+| Non-empty terse and rich strings | ✅ |
+| Full-record uniqueness | ✅ |
+
+## Notes
+
+- 65 terse prompts appear more than once (different rich expansions for same terse). The dataset contract specifies unique *pairs*, not unique terse prompts. Acceptable.
+- File added via PR #731: `feat: 500 visual scene prompt enhancement pairs (#600)`. Merged to main.
+
+## Files Added in This PR
+
+- `tests/test_prompt_enhancement_visual_scenes.py` — regression test validating the dataset meets issue requirements.