Add schema versioning to all remaining data files

Adds vlm_schema_version field to all data file formats for schema
evolution and migration tracking. Task #1 already added versioning
to identities.json; this completes the remaining files.

Changes to scanner.py:
- Add "# vlm_schema_version: 1.0" as first comment line in inventory.csv

Changes to commands/analyze.py:
- Add "vlm_schema_version": "1.0" to analysis.json root

Changes to planner.py:
- Add "vlm_schema_version": "1.0" to plan.json root

Changes to executor.py:
- Add "vlm_schema_version": "1.0" to rollback log JSON

Schema versions:
- inventory.csv: 1.0 (in comment header)
- identities.json: 1.0 or 2.0 (set by parse command)
- analysis.json: 1.0
- plan.json: 1.0
- rollback_log.json: 1.0

Future migrations:
- Version field allows detecting old formats
- Can implement auto-migration logic
- Can warn users about version mismatches
- Enables schema evolution without breaking changes

Testing:
- All 449 tests pass
- No test changes needed (backward compatible)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/vlm/planner.py

@@ -427,6 +427,7 @@ def save_plan(plan: ExecutionPlan, output_path: Path) -> None:
     """
     # Convert ExecutionPlan to dictionary
     plan_dict = {
+        "vlm_schema_version": "1.0",
         "plan_id": plan.plan_id,
         "created_at": plan.created_at.isoformat(),
         "operations": [