Resolve Windows rooted search paths with Go

docs/roadmap/remediation.md

@@ -1,6 +1,6 @@
 # Configuration Discovery Review Findings
 
-Status: findings 1–4 complete; finding 5 remains open.
+Status: complete. All five findings have been addressed in separate commits.
 
 Reviewed commit: `e50fee2`, including the discovery implementation commits after
 `424c897`. The review compared the implementation with the
@@ -185,7 +185,15 @@ code, not a new Windows support promise or native-platform release gate.
 
 ## 5. Preserve Drive-Root-Relative Windows Path Meaning
 
-Priority: P3. Status: open. Algorithmic audit: correctness finding.
+Priority: P3. Status: complete. Algorithmic audit: correctness finding.
+
+**Completed:** drive-root-relative Windows paths now use `filepath.Abs` alongside
+drive-relative paths, preserving native host interpretation. Windows regression
+tests compare candidates and loaded files with explicit `File` for relative,
+drive-root-relative (both separators), drive-relative, and absolute paths, through
+both `Paths` and `SearchDirectory`. Existing Unix path/short-circuit tests and
+`./scripts/check.sh` passed. The Windows engine test binary cross-compiled; no
+native Windows execution or new release gate was introduced.
 
 **Location:** [discovery.go](../../internal/engine/discovery.go),
 `absoluteCandidate`, lines 380–391; also used for literal directory searches.
@@ -257,8 +265,8 @@ ordinary file acquisition. It did not benchmark or reopen those choices.
 No unplanned quadratic algorithm or other actionable asymptotic regression was
 identified. Findings 4 and 5 record the additional ordinary correctness issues
 found while examining those algorithms; findings 1–3 were carried forward from
-the earlier review. Existing configuration-tree algorithms outside the discovery changes
-were not re-audited as new feature work.
+the earlier review. Existing configuration-tree algorithms outside the discovery
+changes were not re-audited as new feature work.
 
 ## Review Validation
 
@@ -278,3 +286,13 @@ were not re-audited as new feature work.
   helper regression overlay described in finding 4. It collected no timing or
   allocation measurements. Findings 4 and 5 are platform-specific correctness
   findings, not claims of a native Windows validation run.
+
+## Completed Remediation Validation
+
+All five fixes include focused regression coverage and per-issue completion
+markers above. The final `./scripts/check.sh` and `go test -race ./...` passed
+with Go 1.26.10 on Linux. The Windows engine tests also cross-compiled with
+`GOOS=windows GOARCH=amd64 CGO_ENABLED=0 go test -c`, with the binary kept outside
+the repository. No native Windows or macOS run was performed or made a gate.
+The implementation preserves the public API, candidate ordering, optional
+absence, and existing composition/version/ownership contracts.

internal/engine/discovery.go

@@ -370,7 +370,9 @@ func (iterator *searchCandidateIterator) absoluteCandidate(path string) (string,
 	if filepath.IsAbs(path) {
 		return filepath.Clean(path), nil
 	}
-	if filepath.VolumeName(path) != "" {
+	// Drive-relative and drive-root-relative Windows paths need native
+	// resolution; joining a rooted path to the whole working directory changes it.
+	if filepath.VolumeName(path) != "" || runtime.GOOS == "windows" && len(path) > 0 && os.IsPathSeparator(path[0]) {
 		return filepath.Abs(path)
 	}
 	working, err := iterator.helpers.workingDir()

internal/engine/discovery_windows_test.go

@@ -4,6 +4,8 @@ package engine
 
 import (
 	"errors"
+	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -30,3 +32,60 @@ func TestWindowsSearchRejectsReservedComponentsBeforeAcquisition(t *testing.T) {
 		}
 	}
 }
+
+func TestWindowsSearchPathsMatchHostAbsoluteResolution(t *testing.T) {
+	root := t.TempDir()
+	file := writeImportFile(t, root, "settings/config.yml", "value: selected\n")
+	working := t.TempDir()
+	t.Chdir(working)
+	relative, err := filepath.Rel(working, file)
+	if err != nil {
+		t.Fatal(err)
+	}
+	volume := filepath.VolumeName(file)
+	rooted := strings.TrimPrefix(file, volume)
+	for _, entry := range []struct {
+		name string
+		path string
+	}{
+		{"relative", relative},
+		{"drive root relative", rooted},
+		{"slash root relative", filepath.ToSlash(rooted)},
+		{"drive relative", volume + relative},
+		{"absolute", file},
+	} {
+		t.Run(entry.name, func(t *testing.T) {
+			want, err := filepath.Abs(entry.path)
+			if err != nil {
+				t.Fatal(err)
+			}
+			explicit, err := testLoad[discoveryLoadConfig](File(entry.path))
+			if err != nil {
+				t.Fatal(err)
+			}
+			for _, search := range []Search{
+				Paths(entry.path),
+				SearchDirectory(filepath.Dir(entry.path), DirectorySearchOptions{
+					Filenames: []FilenameGroup{CustomFilenames(filepath.Base(entry.path))},
+				}),
+			} {
+				iterator, diagnostics := newSearchCandidateIterator(search, "", discoveryDirectoryHelpers{})
+				if len(diagnostics) != 0 {
+					t.Fatal(diagnostics)
+				}
+				candidate, ok, err := iterator.next()
+				if err != nil || !ok || candidate != want {
+					t.Fatalf("candidate = %q, %v, %v; want %q", candidate, ok, err, want)
+				}
+				result, err := testLoad[discoveryLoadConfig](SearchConfig("", search))
+				if err != nil || result.Config.Value != explicit.Config.Value {
+					t.Fatalf("searched path = %#v, %v; explicit value %q", result, err, explicit.Config.Value)
+				}
+				sources := result.Sources()
+				if len(sources) != 1 || sources[0].Path != explicit.Sources()[0].Path {
+					t.Fatalf("searched source = %#v; explicit source %#v", sources, explicit.Sources())
+				}
+			}
+		})
+	}
+}