fix: normalize List.aspx?folderID= to fragment form for yt-dlp

Canvas stores folder links as List.aspx?folderID=X (query param).
yt-dlp's PanoptoList extractor requires List.aspx#folderID="X"
(fragment with quoted ID) to scope the download to that folder.
Without the fragment form it downloaded the entire Panopto instance
(1806 items instead of 3).

Also drop --no-playlist for list URLs since they are intentional
playlists, and use title/%(title)s.%(ext)s output template for them.

internal/panopto/downloader.go

@@ -17,6 +17,27 @@ import (
 	"git.directme.in/Joren/CanvasArchiver/internal/utils"
 )
 
+// normalizePanoptoURL converts the query-param form that Canvas stores
+// (List.aspx?folderID=X) to the fragment form that yt-dlp's PanoptoList
+// extractor understands (List.aspx#folderID="X"). Without this yt-dlp
+// ignores the folder filter and downloads the entire Panopto instance.
+func normalizePanoptoURL(rawURL string) string {
+	parsed, err := url.Parse(rawURL)
+	if err != nil {
+		return rawURL
+	}
+	if strings.Contains(parsed.Path, "List.aspx") {
+		folderID := parsed.Query().Get("folderID")
+		if folderID != "" {
+			// Strip query, set fragment: List.aspx#folderID="<id>"
+			parsed.RawQuery = ""
+			parsed.Fragment = fmt.Sprintf(`folderID="%s"`, folderID)
+			return parsed.String()
+		}
+	}
+	return rawURL
+}
+
 func getYoutubeDLCommand() string {
 	exePath, err := os.Executable()
 	if err == nil {
@@ -192,13 +213,35 @@ func DownloadVideo(httpClient *http.Client, accessToken, courseID, modDir, input
 		fmt.Printf("    [*] Downloading video: %s\n", title)
 
 		ytCmd := getYoutubeDLCommand()
-		cmd := exec.Command(ytCmd,
+
+		// Normalize folder URLs so yt-dlp scopes to the right folder.
+		normalizedURL := normalizePanoptoURL(targetURL)
+
+		// Folder/list URLs are intentional playlists; don't pass --no-playlist.
+		isList := strings.Contains(normalizedURL, "List.aspx")
+		var outputTpl string
+		var args []string
+		if isList {
+			outputTpl = utils.Sanitize(title) + "/%(title)s.%(ext)s"
+			args = []string{
+				"--cookies", cookieFile,
+				"--referer", config.BaseURL + "/",
+				"-P", modDir,
+				"-o", outputTpl,
+				normalizedURL,
+			}
+		} else {
+			outputTpl = utils.Sanitize(title) + ".%(ext)s"
+			args = []string{
 				"--no-playlist",
 				"--cookies", cookieFile,
-			"--referer", config.BaseURL+"/",
+				"--referer", config.BaseURL + "/",
 				"-P", modDir,
-			"-o", utils.Sanitize(title)+".%(ext)s",
+				"-o", outputTpl,
-			targetURL)
+				normalizedURL,
+			}
+		}
+		cmd := exec.Command(ytCmd, args...)
 
 		cmd.Stdout = os.Stdout
 		cmd.Stderr = os.Stderr