chore: remove dead clear_cache from ai.py, deduplicate CACHE_ROOT

- Delete unused clear_cache() from ai.py (luminos.py imports it from
  capabilities.py)
- Remove CACHE_ROOT import from ai.py (was only used by dead function)
- Replace local CACHE_ROOT constant in capabilities.py with import
  from cache.py (single source of truth)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

luminos_lib/ai.py

@@ -25,7 +25,7 @@ import tree_sitter_javascript
 import tree_sitter_rust
 import tree_sitter_go
 
-from luminos_lib.cache import CACHE_ROOT, _CacheManager, _get_investigation_id
+from luminos_lib.cache import _CacheManager, _get_investigation_id
 from luminos_lib.capabilities import check_ai_dependencies
 
 MODEL = "claude-sonnet-4-20250514"
@@ -1382,21 +1382,6 @@ def _run_investigation(client, target, report, show_hidden=False,
     return brief, detailed, flags
 
 
-# ---------------------------------------------------------------------------
-# Cache cleanup
-# ---------------------------------------------------------------------------
-
-def clear_cache():
-    """Remove all investigation caches under /tmp/luminos/."""
-    import shutil
-    if os.path.isdir(CACHE_ROOT):
-        shutil.rmtree(CACHE_ROOT)
-        print(f"Cleared cache: {CACHE_ROOT}", file=sys.stderr)
-    else:
-        print(f"No cache to clear ({CACHE_ROOT} does not exist).",
-              file=sys.stderr)
-
-
 # ---------------------------------------------------------------------------
 # Public interface
 # ---------------------------------------------------------------------------

luminos_lib/capabilities.py

@@ -123,7 +123,7 @@ def print_status():
     print(f"\n  Install all with:\n    pip install {' '.join(all_pkgs)}\n")
 
 
-CACHE_ROOT = "/tmp/luminos"
+from luminos_lib.cache import CACHE_ROOT
 
 
 def clear_cache():