feat: add WSL Windows Terminal support

internal/data/chronicle_windows.go

@@ -5,6 +5,7 @@ package data
 import (
 	"io"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"sync"
 
@@ -51,6 +52,11 @@ func startPTY(binary string) (io.ReadWriteCloser, error) {
 
 // findCopilotBinary returns the path to copilot.exe on Windows.
 func findCopilotBinary() string {
+	// Try PATH first (matches Unix behavior).
+	if p, err := exec.LookPath("copilot"); err == nil {
+		return p
+	}
+
 	candidates := []string{
 		filepath.Join(os.Getenv("ProgramFiles"), "nodejs", "node_modules",
 			"@github", "copilot", "node_modules", "@github", "copilot-win32-x64", "copilot.exe"),

internal/data/mq_coverage_test.go

@@ -166,9 +166,10 @@ func TestLastReindexTime_EmptyWAL(t *testing.T) {
 // ---------------------------------------------------------------------------
 
 func TestFindCopilotBinary_NoCandidates(t *testing.T) {
-	// Set environment to non-existent paths.
+	// Set environment to non-existent paths and isolate PATH.
 	t.Setenv("ProgramFiles", filepath.Join(t.TempDir(), "nonexistent"))
 	t.Setenv("APPDATA", "")
+	t.Setenv("PATH", t.TempDir())
 
 	got := findCopilotBinary()
 	if got != "" {
@@ -179,6 +180,7 @@ func TestFindCopilotBinary_NoCandidates(t *testing.T) {
 func TestFindCopilotBinary_WithAPPDATA(t *testing.T) {
 	tmp := t.TempDir()
 	t.Setenv("ProgramFiles", filepath.Join(tmp, "nonexistent"))
+	t.Setenv("PATH", filepath.Join(tmp, "emptypath"))
 
 	// Create the APPDATA candidate path.
 	appdata := filepath.Join(tmp, "appdata")
@@ -206,6 +208,7 @@ func TestFindCopilotBinary_WithProgramFiles(t *testing.T) {
 	progFiles := filepath.Join(tmp, "Program Files")
 	t.Setenv("ProgramFiles", progFiles)
 	t.Setenv("APPDATA", "")
+	t.Setenv("PATH", filepath.Join(tmp, "emptypath"))
 
 	candidatePath := filepath.Join(progFiles, "nodejs", "node_modules",
 		"@github", "copilot", "node_modules", "@github", "copilot-win32-x64")
@@ -223,6 +226,28 @@ func TestFindCopilotBinary_WithProgramFiles(t *testing.T) {
 	}
 }
 
+func TestFindCopilotBinary_ViaPath(t *testing.T) {
+	tmp := t.TempDir()
+	t.Setenv("ProgramFiles", filepath.Join(tmp, "nonexistent"))
+	t.Setenv("APPDATA", "")
+
+	// Place a copilot.exe on PATH.
+	binDir := filepath.Join(tmp, "bin")
+	if err := os.MkdirAll(binDir, 0o755); err != nil {
+		t.Fatalf("creating bin dir: %v", err)
+	}
+	fakeBinary := filepath.Join(binDir, "copilot.exe")
+	if err := os.WriteFile(fakeBinary, []byte("fake"), 0o755); err != nil {
+		t.Fatalf("writing fake binary: %v", err)
+	}
+	t.Setenv("PATH", binDir)
+
+	got := findCopilotBinary()
+	if got != fakeBinary {
+		t.Errorf("findCopilotBinary() = %q, want %q", got, fakeBinary)
+	}
+}
+
 // ---------------------------------------------------------------------------
 // Maintain — 56% coverage, test error branches
 // ---------------------------------------------------------------------------

internal/platform/paths.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"sync"
 )
 
 const (
@@ -58,20 +59,30 @@ func SessionStorePath() (string, error) {
 const wslMountRoot = "/mnt/c/Users"
 
 // isWSL reports whether the current process is running inside Windows
-// Subsystem for Linux.
+// Subsystem for Linux. The result is cached after the first call since
+// the WSL status cannot change during a process lifetime.
 func isWSL() bool {
-	// WSL2 (and recent WSL1) always set WSL_DISTRO_NAME.
-	if os.Getenv("WSL_DISTRO_NAME") != "" {
-		return true
-	}
-	// Older WSL1 may not set the env var; fall back to /proc/version.
-	data, err := os.ReadFile("/proc/version")
-	if err != nil {
-		return false
-	}
-	return strings.Contains(strings.ToLower(string(data)), "microsoft")
+	wslOnce.Do(func() {
+		// WSL2 (and recent WSL1) always set WSL_DISTRO_NAME.
+		if os.Getenv("WSL_DISTRO_NAME") != "" {
+			wslCached = true
+			return
+		}
+		// Older WSL1 may not set the env var; fall back to /proc/version.
+		data, err := os.ReadFile("/proc/version")
+		if err != nil {
+			return
+		}
+		wslCached = strings.Contains(strings.ToLower(string(data)), "microsoft")
+	})
+	return wslCached
 }
 
+var (
+	wslOnce   sync.Once
+	wslCached bool
+)
+
 // findWindowsSessionStore scans Windows user-profile directories under the
 // default WSL mount for a Copilot session store database.
 func findWindowsSessionStore() string {