Apply P2: import qualification and code cleanup

P2 - Import Qualification & Code Cleanup:
- ext/TestRunner.jl: using DocStringExtensions → import DocStringExtensions: TYPEDEF, TYPEDSIGNATURES
- ext/CoveragePostprocessing.jl: using Coverage → using Coverage: Coverage
- Removed dead ternary branches (ext/TestRunner.jl:447, 332)
- Fixed byte-indexing path slicing → use relpath() (ext/CoveragePostprocessing.jl:347)
- Fixed collision risk in cov file flattening → use normalized flat names (ext/CoveragePostprocessing.jl:221)

All tests pass: 1161/1161

Author: ocots

ext/CoveragePostprocessing.jl

@@ -10,7 +10,7 @@ Most functions in this module have filesystem side effects.
 module CoveragePostprocessing
 
 using CTBase: CTBase
-using Coverage
+using Coverage: Coverage
 
 # Main entry point for coverage post-processing
 """
@@ -218,14 +218,8 @@ function _collect_and_move_cov_files!(source_dirs, dest_dir)
                 # But let's stick to the plan: just recursive collection.
 
                 src = joinpath(root, f)
-                dest = joinpath(dest_dir, f) # Wait, this might fail if f is just filename.
-
-                # The issue with joinpath(dest_dir, f) if f is just a filename is that it puts everything in root of dest_dir.
-                # If f comes from walkdir's `files`, it is just the filename.
-                # So `src` is correct. `dest` puts it in `coverage/cov/filename.cov`. 
-                # This matches previous behavior, just expanded to subdirs.
-
-                dest = joinpath(dest_dir, f)
+                flat = replace(relpath(src, dir), r"[/\\]" => "_")
+                dest = joinpath(dest_dir, flat)
                 mv(src, dest; force=true)
                 push!(moved, dest)
             end
@@ -347,12 +341,8 @@ function _generate_coverage_reports!(
 
     # Helper to make paths relative to root_dir
     function relative_path(path, root)
-        if startswith(path, root)
-            relpath = path[(length(root) + 1):end]
-            # Remove leading slash if present
-            return startswith(relpath, "/") ? relpath[2:end] : relpath
-        end
-        return path
+        startswith(path, root) || return path
+        return relpath(path, root)
     end
 
     function write_report(io)

ext/TestRunner.jl

@@ -10,7 +10,7 @@ running testsets).
 module TestRunner
 
 using CTBase: CTBase
-using DocStringExtensions
+import DocStringExtensions: TYPEDEF, TYPEDSIGNATURES
 using Test: Test, @testset
 
 """
@@ -327,7 +327,7 @@ julia> TestRunner._normalize_selections(
 ```
 """
 function _normalize_selections(selections::Vector{String}, candidates::Vector{<:TestSpec})
-    candidate_strs = [c isa Symbol ? String(c) : String(c) for c in candidates]
+    candidate_strs = [String(c) for c in candidates]
     normalized = String[]
     for sel in selections
         # Strip trailing slash(es)
@@ -442,7 +442,7 @@ julia> TestRunner._builder_to_string("utils")
 ```
 """
 function _builder_to_string(x)
-    x isa Symbol ? String(x) : String(x)
+    String(x)
 end
 
 """