Fix CI workflow: Add tree-sitter CLI installation and fix linting errors

vibeguard/cli/commands/report.py

@@ -1,6 +1,5 @@
 """Report command for VibeGuard CLI."""
 
-from pathlib import Path
 from typing import Any
 
 import click
@@ -22,7 +21,6 @@ def report(
     output_sarif: str | None,
 ) -> None:
     """Generate reports from VibeGuard analysis results."""
-    config = ctx["config"]
     console = ctx["console"]
 
     generator = ReportGenerator()
@@ -33,8 +31,6 @@ def report(
         return
 
     if output_json:
-        import json
-
         console.print_json(data=issues)
     elif output_html:
         generator.generate_html(issues, output_html)