Added robust guards to detect_directory_languages() by introducing depth, file count, and timeout controls. Defaults and validations are implemented to prevent resource exhaustion during LSP discovery.

- Added max_depth parameter (default: 50) with validation to ensure a positive integer.
- Added max_files parameter (default: 10,000) with validation to ensure a positive integer.
- Added timeout parameter (default: 30.0 seconds) with validation to ensure a positive float.
- Pass followlinks=False to os.walk() to prevent symlink-based DoS via recursive loops.
- Implemented depth tracking in the traversal loop with early break when max_depth is exceeded.
- Implemented file count tracking with early break when max_files is exceeded.
- Implemented periodic timeout checks during traversal to enforce the overall time limit.
- Added warning logging when traversal is terminated early due to any limit.
- Updated the function docstring to document the new parameters and their defaults.
- Created comprehensive BDD tests in features/lsp_discovery_dos_protection.feature to validate the protections.

ISSUES CLOSED: #7161

@@ -0,0 +1,83 @@
+Feature: LSP language discovery DoS protection
+  Prevent resource exhaustion attacks via directory traversal limits.

@@ -0,0 +90,4 @@
+    patcher_walk = patch(
+        "cleveragents.lsp.discovery.os.walk",
+        side_effect=capture_walk,
+    )

@@ -0,0 +1,85 @@
+Feature: LSP language discovery DoS protection

@@ -0,0 +1,85 @@
+Feature: LSP language discovery DoS protection