test(coverage): add Behave scenarios for 39 under-covered modules

Add Behave feature/step pairs that exercise uncovered branches across handlers, LSP, CLI, and service layers to reach the coverage gate.

ISSUES CLOSED: #1232

features/lsp_discovery_coverage.feature

@@ -0,0 +1,105 @@
+Feature: LSP language discovery coverage
+  Exercise uncovered lines in src/cleveragents/lsp/discovery.py
+  covering shebang detection, cache behaviour, directory scanning,
+  special-name detection, UKO layer, and server matching.
+
+  # ------------------------------------------------------------------
+  # Layer 2 – shebang detection edge cases (lines 142, 146, 157)
+  # ------------------------------------------------------------------
+
+  Scenario: Shebang returns None for non-shebang line
+    Given ldcov a first line "echo hello"
+    When ldcov I detect from shebang
+    Then ldcov the shebang result is None
+
+  Scenario: Shebang returns None for bare hashbang
+    Given ldcov a first line "#!"
+    When ldcov I detect from shebang
+    Then ldcov the shebang result is None
+
+  Scenario: Shebang returns None for empty hashbang with whitespace
+    Given ldcov a first line "#!  "
+    When ldcov I detect from shebang
+    Then ldcov the shebang result is None
+
+  Scenario: Shebang returns None for unknown interpreter
+    Given ldcov a first line "#!/usr/bin/unknownlang"
+    When ldcov I detect from shebang
+    Then ldcov the shebang result is None
+
+  # ------------------------------------------------------------------
+  # Cache hit (line 201)
+  # ------------------------------------------------------------------
+
+  Scenario: detect_file_language returns cached result on second call
+    Given ldcov a LanguageDiscovery instance
+    And ldcov the cache already contains "/tmp/cached.py" mapped to "python"
+    When ldcov I detect file language for "/tmp/cached.py"
+    Then ldcov the detected language is "python"
+
+  # ------------------------------------------------------------------
+  # invalidate_all (line 246)
+  # ------------------------------------------------------------------
+
+  Scenario: invalidate_all clears the entire cache
+    Given ldcov a LanguageDiscovery instance
+    And ldcov the cache already contains "/a.py" mapped to "python"
+    And ldcov the cache already contains "/b.rs" mapped to "rust"
+    When ldcov I call invalidate_all
+    Then ldcov the cache is empty
+
+  # ------------------------------------------------------------------
+  # Special basenames – Makefile (line 257), CMakeLists.txt (line 259)
+  # ------------------------------------------------------------------
+
+  Scenario: Makefile is detected as makefile language
+    Given ldcov a LanguageDiscovery instance
+    When ldcov I detect uncached language for "project/Makefile"
+    Then ldcov the detected language is "makefile"
+
+  Scenario: CMakeLists.txt is detected as cmake language
+    Given ldcov a LanguageDiscovery instance
+    When ldcov I detect uncached language for "project/CMakeLists.txt"
+    Then ldcov the detected language is "cmake"
+
+  # ------------------------------------------------------------------
+  # Layer 3 – UKO classification (line 276)
+  # ------------------------------------------------------------------
+
+  Scenario: UKO classification is used when extension and shebang miss
+    Given ldcov a LanguageDiscovery instance with UKO mapping "/data/blob" to "python"
+    When ldcov I detect uncached language for "/data/blob"
+    Then ldcov the detected language is "python"
+
+  # ------------------------------------------------------------------
+  # Directory scanning (lines 219-231, 234)
+  # ------------------------------------------------------------------
+
+  Scenario: detect_directory_languages finds languages in a tree
+    Given ldcov a LanguageDiscovery instance
+    And ldcov a mock directory tree with files "app.py,lib.rs,readme.txt"
+    When ldcov I detect directory languages
+    Then ldcov the directory languages include "python"
+    And ldcov the directory languages include "rust"
+
+  Scenario: detect_directory_languages handles OSError gracefully
+    Given ldcov a LanguageDiscovery instance
+    And ldcov os.walk will raise an OSError
+    When ldcov I detect directory languages for "/nonexistent"
+    Then ldcov the directory languages result is an empty list
+
+  # ------------------------------------------------------------------
+  # get_servers_for_language (lines 298-301)
+  # ------------------------------------------------------------------
+
+  Scenario: get_servers_for_language filters matching configs
+    Given ldcov a LanguageDiscovery instance
+    And ldcov server configs with languages "python,rust" and "javascript"
+    When ldcov I get servers for language "python"
+    Then ldcov the matched server count is 1
+
+  Scenario: get_servers_for_language returns empty for no match
+    Given ldcov a LanguageDiscovery instance
+    And ldcov server configs with languages "python,rust" and "javascript"
+    When ldcov I get servers for language "haskell"
+    Then ldcov the matched server count is 0