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

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+# 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.

tests/test_prompt_enhancement_visual_scenes.py

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+#!/usr/bin/env python3
+"""
+Verification test for issue #600: Prompt Enhancement — Visual Scenes 500 pairs.
+
+This test confirms that the visual-scenes-500.jsonl dataset exists on main
+and satisfies the requirements defined in the Training Factory specification.
+
+Acceptance criteria:
+- 500 JSONL records
+- Each record: {"terse": str, "rich": str, "domain": "visual scenes"}
+- All fields non-empty strings
+- All records have correct domain value
+
+Evidence: dataset present at training/data/prompt-enhancement/visual-scenes-500.jsonl
+Branch: main (merged via PR #731)
+"""
+
+import json
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+DATASET_PATH = REPO_ROOT / "training" / "data" / "prompt-enhancement" / "visual-scenes-500.jsonl"
+
+
+def test_dataset_file_exists():
+    """Verify the visual scenes dataset file exists."""
+    assert DATASET_PATH.exists(), (
+        f"Missing dataset file: {DATASET_PATH}. "
+        "Run the visual scene prompt enhancement worker to generate 500 pairs."
+    )
+
+
+def test_dataset_has_500_records():
+    """Verify exactly 500 records are present."""
+    with open(DATASET_PATH) as f:
+        lines = f.readlines()
+    assert len(lines) == 500, f"Expected 500 records, got {len(lines)}"
+
+
+def test_all_records_valid_json():
+    """Verify every line parses as valid JSON."""
+    records = []
+    with open(DATASET_PATH) as f:
+        for i, line in enumerate(f, 1):
+            try:
+                rec = json.loads(line)
+                records.append(rec)
+            except json.JSONDecodeError as e:
+                assert False, f"Line {i}: invalid JSON: {e}"
+    assert len(records) == 500
+
+
+def test_each_record_has_required_fields():
+    """Verify terse, rich, domain fields exist and are non-empty strings."""
+    with open(DATASET_PATH) as f:
+        for i, line in enumerate(f, 1):
+            rec = json.loads(line)
+            terse = rec.get("terse")
+            rich = rec.get("rich")
+            domain = rec.get("domain")
+            assert isinstance(terse, str) and terse.strip(), (
+                f"Line {i}: missing or empty 'terse' field"
+            )
+            assert isinstance(rich, str) and rich.strip(), (
+                f"Line {i}: missing or empty 'rich' field"
+            )
+            assert isinstance(domain, str) and domain.strip(), (
+                f"Line {i}: missing or empty 'domain' field"
+            )
+
+
+def test_domain_value_is_visual_scenes():
+    """Verify every record's domain is exactly 'visual scenes'."""
+    with open(DATASET_PATH) as f:
+        for i, line in enumerate(f, 1):
+            rec = json.loads(line)
+            assert rec["domain"] == "visual scenes", (
+                f"Line {i}: domain '{rec['domain']}' != 'visual scenes'"
+            )
+
+
+def test_record_uniqueness():
+    """Verify each JSON record (full object) is unique."""
+    records = []
+    with open(DATASET_PATH) as f:
+        for line in f:
+            records.append(json.loads(line))
+    unique = {json.dumps(rec, sort_keys=True) for rec in records}
+    assert len(unique) == 500, (
+        f"Duplicate records found: {500 - len(unique)} record(s) are not unique"
+    )