fix: handle itch.zone serving PNG for .jpg URLs

itch.zone returns content-type: image/png for .jpg URLs. HTTPImageFetcher
uses URL extension to pick the decoder, causing load_jpg_from_buffer to
fail on PNG data. Added format detection fallback that checks Content-Type
headers when the normal fetch fails for .jpg/.jpeg URLs.

Bump to v0.1.16

core/boxart_itch.gd

@@ -22,6 +22,7 @@ const LOG_URL_MAX_LEN := 80
 const SETTING_SECTION := "plugin.artprovider"
 const SETTING_ANIMATED_GIFS := "animated_gifs"
 const GIF_DEFAULT_FRAME_DELAY_MS := 100
+const CACHE_DIR := "images"
 
 @export var use_caching: bool = true
 var http_image := HTTPImageFetcher.new()
@@ -118,6 +119,71 @@ func _is_gif_url(url: String) -> bool:
 	return _sanitize_url(url).to_lower().ends_with(".gif")
 
 
+## Returns whether a URL points to a JPEG image.
+func _is_jpg_url(url: String) -> bool:
+	var clean := _sanitize_url(url).to_lower()
+	return clean.ends_with(".jpg") or clean.ends_with(".jpeg")
+
+
+## Removes and frees an HTTPRequest node.
+func _remove_http(http: HTTPRequest) -> void:
+	remove_child(http)
+	http.queue_free()
+
+
+## Downloads an image and detects the actual format from content-type headers.
+## Used as a fallback when HTTPImageFetcher fails due to extension mismatch.
+func _fetch_image_with_format_detection(url: String, cache_flags: int) -> Texture2D:
+	var http := HTTPRequest.new()
+	http.timeout = HTTP_TIMEOUT_MS / 1000.0
+	add_child.call_deferred(http)
+	await http.ready
+
+	if http.request(url) != OK:
+		_remove_http(http)
+		return null
+
+	var args: Array = await http.request_completed
+	var result: int = args[0]
+	var response_code: int = args[1]
+	var headers: PackedStringArray = args[2]
+	var body: PackedByteArray = args[3]
+	_remove_http(http)
+
+	if result != HTTPRequest.RESULT_SUCCESS or response_code != 200:
+		return null
+
+	# Detect actual format from Content-Type header.
+	var content_type := ""
+	for h in headers:
+		if h.to_lower().begins_with("content-type:"):
+			content_type = h.split(":", true, 1)[1].strip_edges().to_lower()
+			break
+
+	var image := Image.new()
+	var err: int = ERR_INVALID_DATA
+	if content_type.find("png") != -1:
+		err = image.load_png_from_buffer(body)
+	elif content_type.find("jpeg") != -1 or content_type.find("jpg") != -1:
+		err = image.load_jpg_from_buffer(body)
+	elif content_type.find("webp") != -1:
+		err = image.load_webp_from_buffer(body)
+	else:
+		# Unknown type — try PNG first, then JPEG.
+		err = image.load_png_from_buffer(body)
+		if err != OK:
+			err = image.load_jpg_from_buffer(body)
+
+	if err != OK:
+		logger.warn("Format detection failed for %s (content-type: %s)" % [url.left(LOG_URL_MAX_LEN), content_type])
+		return null
+
+	var texture := ImageTexture.create_from_image(image)
+	if cache_flags & Cache.FLAGS.SAVE:
+		Cache.save_image(CACHE_DIR, url, texture)
+	return texture
+
+
 func get_boxart(item: LibraryItem, kind: LAYOUT) -> Texture2D:
 	if not kind in layout_map:
 		logger.error("Unsupported boxart layout: {0}".format([kind]))
@@ -373,7 +439,13 @@ func _fetch_image(url: String, cache_flags: int) -> Texture2D:
 			_last_animated_setting = animated
 			logger.info("Animated GIF setting changed to %s — cache cleared" % str(animated))
 		return await _fetch_gif_as_texture(url, cache_flags)
-	return await http_image.fetch(url, cache_flags)
+	# HTTPImageFetcher uses the URL extension to pick the decoder, but
+	# itch.zone often serves PNG data for .jpg URLs. If the normal fetch
+	# fails for a .jpg/.jpeg URL, retry by detecting the actual format.
+	var texture := await http_image.fetch(url, cache_flags)
+	if texture == null and _is_jpg_url(url):
+		texture = await _fetch_image_with_format_detection(url, cache_flags)
+	return texture
 
 
 ## Downloads a GIF and converts it to a Godot texture. When animated GIFs